{"id":29,"date":"2024-06-16T14:08:18","date_gmt":"2024-06-16T14:08:18","guid":{"rendered":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/?post_type=chapter&#038;p=29"},"modified":"2024-09-30T17:21:21","modified_gmt":"2024-09-30T17:21:21","slug":"chapter-4-screening-and-diagnostic-tests","status":"publish","type":"chapter","link":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/chapter\/chapter-4-screening-and-diagnostic-tests\/","title":{"raw":"Chapter 4 Screening and Diagnostic Tests","rendered":"Chapter 4 Screening and Diagnostic Tests"},"content":{"raw":"<h2>Overview<\/h2>\r\nDiagnostic tests and health screenings have a vital role to play in the surveillance of disease in patients, communities, and from a public health perspective.\u00a0 By helping to identify disease early, treatment and interventions can begin in the fight against chronic and infectious disease.\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Learning Objectives<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nBy the end of this chapter, you will be able to:\r\n<ul>\r\n \t<li>Know the three primary disease prevention strategies<\/li>\r\n \t<li>Differentiate between screening and diagnostic testing used to determine disease risk<\/li>\r\n \t<li>Know the types and methods of screening programs used for common causes of mortality in communities<\/li>\r\n \t<li>Understand the role of screening programs in public health<\/li>\r\n \t<li>Understand the link between disease screening and types of validity testing<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\nThe Three Disease Prevention Strategies\r\n\r\nPrimary Prevention\r\n\r\nPrimary prevention consists of measures aimed at a susceptible population or individual. The purpose of primary prevention is to prevent a disease from ever occurring. Primary prevention targets\u00a0 healthy individuals.\u00a0 Activities that limit risk exposure or increase the immunity of individuals at risk help prevent a disease from progressing .\u00a0 Examples of primary prevention include immunizations, use of condoms, abstinence education, and emergency contraception.\r\n\r\nSecondary Prevention\r\n\r\nSecondary prevention emphasizes early disease detection, and it targets\u00a0 healthy-appearing individuals with subclinical forms of the disease. The subclinical disease consists of pathologic changes but no overt symptoms that are diagnosable in a doctor's visit. Secondary prevention often occurs in the form of screenings. For example, a Pap smear is a form of secondary prevention aimed to diagnose cervical cancer\u00a0 before progression.\r\n\r\nTertiary Prevention\r\n\r\nTertiary prevention targets both the clinical symptoms or screening results and outcome stages of a disease. It is implemented in patients with symptoms and aims to reduce the severity of the disease as well as any associated disease rebound. While secondary prevention seeks to prevent the onset of illness, tertiary prevention aims to reduce the effects of the disease symptoms once established in an individual.\u00a0 Tertiary prevention examples include rehabilitation efforts for cardiac concerns and strokes.\r\n\r\nOverview of Diagnosis\r\n\r\nDiagnosis is the act or process of determining or identifying the nature and cause of disease or injury through the following: evaluation of patient history, examination of the patient and review of laboratory or screening results. <a href=\"#_ftn1\">[1]<\/a>\r\n\r\nOverview of Screenings\r\n\r\nScreening of disease involves using tests or procedures to identify disease or health concerns.\u00a0 Screening is most often done on individuals who are often well and do not have any observable signs or symptoms of disease.\u00a0 Most individuals getting screenings done are not aware that an illness is not detected or risk factors for disease exist.\u00a0 Often these screenings are done in combination with disease surveillance, the collection of morbidity or mortality data in a population.\r\n\r\nScreening is not the same as diagnosis, but some screening tests are done as diagnostic testing to identify disease or disease risk.\u00a0 Screenings are medical tests that doctors use to check for diseases and health conditions before there are any signs and symptoms.\u00a0 Screenings help find problems early, allowing opportunity for earlier and possibly easier treatment of diseases.\r\n\r\nGetting recommended screenings is one of the most important things you can do for. Your health.\u00a0 Depending on your age, sex, and medical history, you may need to be screened for various health diseases or conditions.\u00a0 See Table 4.4 for recommended screening exams your doctor may encourage you to consider.\r\n\r\nThere are concerns with screening tests which include false-positive results (the wrong results) , over diagnosis of potentially benign conditions, and at times access to the tests may prove challenging for those needing the screening.\u00a0 The benefits of possible early diagnosis, early treatment, and preventive treatment outweigh the concerns some have with screenings.\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td>What Screening Tests and Results are Used for<\/td>\r\n<td>What Diagnostic Tests and Results are Used for<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>To detect diseases in the early stages<\/td>\r\n<td>To detect the presence or absence of disease<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Used for asymptomatic individuals especially those with Higer risks<\/td>\r\n<td>Used for individuals who have symptoms to help diagnose disease or with asymptomatic individuals with a positive screening test<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Depending on the results the screening test would indicate a high or lower probability or risk of disease<\/td>\r\n<td>The result of the diagnostic test is more likely able to provide a definite disease diagnosis<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTable 4.1: The Main Differences Between Screening Testa and results and Diagnostic Tests and Results\r\n\r\nTwo Types of Screenings\r\n\r\nDisease screening programs have a long history in strategies to control infectious disease epidemics and target chronic disease treatments.\u00a0 There are two types of screenings that help with collecting information that can help address the major causes of morbidity and mortality. These two screening efforts are mass screening and selective screening.\r\n\r\nMass screenings\u00a0 are tests that are administered to total populations groups regardless of disease risk.\u00a0 Some examples of these tests include TB tests, urinalysis, drug screenings, measuring temperatures of individuals to determine possible infection risk, eye exams, pap smears and mammograms.\r\n\r\nSelective screenings are tests administered to high-risk population groups.\u00a0 These screening tests are used to help diagnose and detect infectious diseases, chronic diseases, and other conditions in individuals who have specific risk factors.\u00a0 These may be individuals who smoke, are obese, use IV drugs, or engage in unprotected sex or are at increased risk for adverse health concerns or outcomes.\u00a0 Regular screening of these individuals will help better diagnose and treat for possible disease concerns.\r\n\r\nEnsuring Screenings help with Disease Diagnosis\r\n\r\nFor screening tests to be considered useful as well as necessary or recommended, they need to demonstrate reliability and validity.\r\n\r\nReliability is the degree to which an instrument can produce consistent results and consistent results on different occasions when there is no evidence of change. This type of measurement is often about the precision of the testing. <a href=\"#_ftn4\">[3]<\/a> Validity is the degree to which an instrument measures what it is supposed to measure, and that the measurement is accurate.\r\n\r\nThe Gold Standard with any type of screening or medical testing is the definitive diagnosis.\u00a0 This would happen when the diagnosis has been determined by surgery, biopsy, autopsy, or other testing methods.\u00a0 These tests are what are used by many health professionals for verifying, confirming and diagnosis.\r\n\r\nScreening measures need to be valid, reliable, and meet the gold standard for testing.\u00a0 When they are patient and health professionals can strategize treatment and care helping to limit morbidity and mortality risks.\r\n<table>\r\n<tbody>\r\n<tr>\r\n<td>Type of Diagnostic Test<\/td>\r\n<td>Testing Examples<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Laboratory Tests<\/td>\r\n<td>Blood, urine sampling<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Imaging Tests<\/td>\r\n<td>CT scan, MRI, Mammography<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Endoscopy<\/td>\r\n<td>Colonoscopy, Bronchoscopy<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Biopsy<\/td>\r\n<td>Lump or node removal, tissue or cell testing<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTable 4.3: Four Types of Diagnostic Tests and Examples\r\n\r\n<img class=\"alignnone size-medium wp-image-57\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" \/><img class=\"alignnone size-medium wp-image-58\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" \/><img class=\"alignnone size-medium wp-image-59\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" \/>\r\n\r\nTable 4.4:Recommended Screening Exams\/Schedule\r\n\r\nScreening Calculations for Validity\r\n\r\nThere are four measures of validity when looking at screening measures.\u00a0 Sensitivity, specificity, positive predictive value and negative predictive value.\u00a0 These four measures are described in the table below.\r\n\r\nWhen using these measures to determine if screening tests are valid, you must consider false positive and false negative results.\u00a0 False positive results may warrant unnecessary medical tests to further investigate results.\u00a0 Patients may experience anxiety because of the false positive result, only to find out that they do not have the disease.\u00a0 With false negative results, the disease is not detected in a patient who has the disease and the disease progresses.\u00a0 Being aware of these issues with screenings is important for patients to understand.\r\n<table style=\"border-collapse: collapse;width: 100%\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 31px\">\r\n<td style=\"height: 31px;width: 19.9782%\">Type of Screening \u00a0Test Validity Measures<\/td>\r\n<td style=\"height: 31px;width: 46.6157%\">Description<\/td>\r\n<td style=\"width: 33.3333%\">Calculation<\/td>\r\n<\/tr>\r\n<tr style=\"height: 10px\">\r\n<td style=\"height: 10px;width: 19.9782%\">Sensitivity<\/td>\r\n<td style=\"height: 10px;width: 46.6157%\">The ability of the test to identify the presence of a disease or illness correctly; True positive and true negative results<\/td>\r\n<td style=\"width: 33.3333%\"><img class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-8d96d4d7e14d93fff5771b5ad4a51906_l3.svg\" alt=\"\\text { Sensitivity }=\\frac{A}{A+C}\" width=\"145\" height=\"25\" \/><\/td>\r\n<\/tr>\r\n<tr style=\"height: 31px\">\r\n<td style=\"height: 31px;width: 19.9782%\">Specificity<\/td>\r\n<td style=\"height: 31px;width: 46.6157%\">The ability of a test to identify the absence of a disease or illness correctly; True negative or false positive results<\/td>\r\n<td style=\"width: 33.3333%\"><img class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-a1020c819e936ac2388fac2debfefad4_l3.svg\" alt=\"\\text { Specificity }=\\frac{D}{B+D}\" width=\"145\" height=\"24\" \/><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 19.9782%\">Positive Predictive Values (PPV)<\/td>\r\n<td style=\"height: 15px;width: 46.6157%\">The likelihood a person who has a positive test result does have the disease or illness<\/td>\r\n<td class=\"column-3\" style=\"width: 33.3333%\"><img class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-c097c212a2f527e70e566942f6e21823_l3.svg\" alt=\"\\text { Predictive value positive }=\\frac{A}{A+B}\" width=\"254\" height=\"25\" \/><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 19.9782%\">Negative Predictive Value (NPV)<\/td>\r\n<td style=\"height: 15px;width: 46.6157%\">The likelihood a person who has a negative test result indeed does not have the disease or illness<\/td>\r\n<td class=\"column-3\" style=\"width: 33.3333%\"><img class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-f172127158c952941aba24da89ba881a_l3.svg\" alt=\"\\text { Predictive value negative }=\\frac{D}{C+D}\" width=\"259\" height=\"24\" \/><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTable 4.5 The Four Measures of Screening Test Validity\r\n\r\nThe presentation of diagnostic exam results is often in 2x2 tables, such as Table 4.6.\u00a0 The values within this table can help to determine sensitivity and specificity, as well as other epidemiologic value data.\r\n\r\n<img class=\"alignnone wp-image-77 size-medium\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-300x88.jpeg\" alt=\"Diagnostic testing 2x2 accuracy table\" width=\"300\" height=\"88\" \/>\r\n\r\nTable 4.6 Diagnostic Testing 2x2 Accuracy Table\r\n\r\nSensitivity and Specificity Testing\r\n\r\nIn epidiemiology, sensitivity and specificity are mathematical calculations used to describe the accuracy of a test that reports the presence or absence of a disease or medical condition.\r\n\r\nIf individuals who have a disease or medical condition are identified as \"positive\" and those who are not are identified as \"negative\" , then sensitivity is a measure of how well the test can identify the positives and specificity is a measure of how well a test can measure the\u00a0 negatives.\r\n\r\n&nbsp;\r\n<div id=\"_O8OzZpmONIOV5OMPvtC-2Ag_65\" class=\"bCOlv\" data-ved=\"2ahUKEwjZl6Cux-OHAxWDCnkGHT6oD4sQkLgIKAZ6BAgoEBA\">\r\n<div class=\"IZE3Td\">\r\n<div data-ved=\"2ahUKEwjZl6Cux-OHAxWDCnkGHT6oD4sQoPIHegQIKBAR\">\r\n<div class=\"PZPZlf\" data-attrid=\"lab\/content\/Sensitivity\">\r\n<div id=\"O8OzZpmONIOV5OMPvtC-2Ag__68\">\r\n<div class=\"wDYxhc NFQFxe viOShc LKPcQc\" data-md=\"471\">\r\n<div class=\"V3FYCf\">\r\n<div class=\"wDYxhc\" data-md=\"61\">\r\n<div class=\"LGOjhe\" role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\"><span class=\"BxUVEf ILfuVd\" lang=\"en\"><span class=\"hgKElc\">Sensitivity is the percentage of people with the disease who are correctly identified by the test. Specificity is the percentage of people without the disease who are correctly excluded by the test. These concepts have clinical importance\u00a0 in helping to\u00a0 confirm or exclude disease during screening.<\/span><\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">In medical screening and diagnosis, test sensitivity is the ability of a test to correctly identify individuals with disease ( true positives), where test specificity is the ability of a test to correctly identify those who do not have disease ( true negatives).<\/div>\r\n<\/div>\r\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Examples of Test Sensitivity and Specificity<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nIf 100 individuals who were screened have a disease and 53 test positive, then the test has a 53% sensitivity.\u00a0 If 100 individuals with no disease are screened and 92 return a negative result, then the test has a 92% specificity.\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>\r\n<div class=\"wDYxhc NFQFxe viOShc LKPcQc\" data-md=\"471\">\r\n<div class=\"V3FYCf\">\r\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">A test which accurately and reliably detects the presence of a disease or a medical condition resulting in a high number of true positives and a low number of true negatives has a high sensitivity.\u00a0 A test that excludes individuals who do not have the disease or medical condition, resulting in a high number or true negatives and a low number of false positives, will have a high specificity.<\/div>\r\n<\/div>\r\n<\/div>\r\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example: Hepatitis A Blood Test for Sensitivity and Specificity in a Population<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nA healthcare provider uses a blood test to determine whether or not individuals have Hepatitis A:\r\n<ul>\r\n \t<li style=\"list-style-type: none\">\r\n<ul>\r\n \t<li class=\"half_rhythm\">\r\n<div>A total of 1,000 individuals had their blood tested for Hepatitis A.<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>427 individuals had positive findings, and 573 individuals had negative findings.<\/div><\/li>\r\n \t<li class=\"half_rhythm\">Out of the 427 individuals who had positive findings, 369 of them had the disease.<\/li>\r\n \t<li>Out of the 573 individuals who had negative findings, 558 did not have the disease.<\/li>\r\n \t<li class=\"half_rhythm\">The healthcare provider found that a total of 384 individuals actually had the disease,<\/li>\r\n \t<li class=\"half_rhythm\">So how accurate was the Hepatitis A blood test in the 1000 individuals?<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Using the 2X2 table approach to sort this data, the following chart:<\/li>\r\n<\/ul>\r\n<table style=\"border-collapse: collapse;width: 100%;height: 60px\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 25%;height: 15px\">Blood Test Results<\/td>\r\n<td style=\"width: 25%;height: 15px\">Hepatitis A Present<\/td>\r\n<td style=\"width: 25%;height: 15px\">Hepatitis A Not Present<\/td>\r\n<td style=\"width: 25%;height: 15px\">Total<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 25%;height: 15px\">Positive<\/td>\r\n<td style=\"width: 25%;height: 15px\">369(A)<\/td>\r\n<td style=\"width: 25%;height: 15px\">58(B)<\/td>\r\n<td style=\"width: 25%;height: 15px\">427<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 25%;height: 15px\">Negative<\/td>\r\n<td style=\"width: 25%;height: 15px\">15(C)<\/td>\r\n<td style=\"width: 25%;height: 15px\">558(D)<\/td>\r\n<td style=\"width: 25%;height: 15px\">573<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 25%;height: 15px\">Total<\/td>\r\n<td style=\"width: 25%;height: 15px\">384(A+C)<\/td>\r\n<td style=\"width: 25%;height: 15px\">616(B+D)<\/td>\r\n<td style=\"width: 25%;height: 15px\">1000<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<ul>\r\n \t<li>Calculation Results for Sensitivity and Specificity:<\/li>\r\n<\/ul>\r\n<i>Sensitivity<\/i>\r\n<ul>\r\n \t<li class=\"half_rhythm\">\r\n<div>Sensitivity=(True Positives (A))\/(True Positives (A)+False Negatives (C))<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Sensitivity=(369 (A))\/(369(A)+15 (C))<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Sensitivity=369\/384<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Sensitivity=0.961 or 96.1%<\/div><\/li>\r\n<\/ul>\r\n<i>Specificity<\/i>\r\n<ul>\r\n \t<li class=\"half_rhythm\">\r\n<div>Specificity=(True Negatives (D))\/(True Negatives (D)+False Positives (B))<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Specificity=(558\u00a0(D))\/(558(D)+58 (B))<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Specificity=558\/616<\/div><\/li>\r\n \t<li class=\"half_rhythm\">\r\n<div>Specificity=0.906 or 90.6%<\/div><\/li>\r\n<\/ul>\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\nCommunity and Public Health Benefits of Screening Programs\r\n\r\nDisease screening programs have a long history in strategies to control infectious disease epidemics and target chronic disease treatments. <a href=\"#_ftn2\">[2]<\/a> Goals of public health screening programs need to be clearly specified and shown to impact case findings.\r\n\r\nUnderstanding the natural history of the disease, knowing what interventions and treatments the scientific and medical community believe work for individuals determined to have disease and finding or having evidence that early intervention improves outcomes are all important considerations for a well-organized public health screening effort.\r\n\r\nScreening programs should measure conditions that can control possible epidemics of infectious disease and target treatment for chronic diseases.\u00a0 Understanding the tangible public health benefits of screening efforts boost confidence that the health care system is working and that all patients have been treated fairly and if needed will benefit from treatment that should be made accessible to them.\r\n<table style=\"border-collapse: collapse;width: 100%\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 100%\">Tangible Public Health Benefits of Screening Programs\r\n<ol>\r\n \t<li>Help control epidemics of infectious disease<\/li>\r\n \t<li>Target treatment for chronic disease<\/li>\r\n \t<li>Early diagnosis and better management of chronic diseases<\/li>\r\n \t<li>Improve health and quality of life of populations and communities<\/li>\r\n<\/ol>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTable 4.2: Tangible Public Health Benefits of Screening Programs\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">The WHO, World Health Organization, states that screening programs should be done only for diseases with serious consequences, screening programs should have clear benefits to people\u2019s health, and screenings should be reliable and not harmful.\u00a0 It is also critical that effective treatments for disease identified in early stages during screening have clear evidence that the treatment is more effective when started before symptoms arise like with Breast Cancer. The public should always have information available to them on screening options and make informed decisions on whether they want to have the screening test. [<\/span><a style=\"text-align: initial;font-size: 1em\" href=\"#_ftn3\">3]<\/a>\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Key Takeaways<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nIn this chapter you learned about disease prevention strategies, screenings for disease, and diagnostic tests to confirm chronic and infectious diseases.\u00a0 Screening calculations, validity and understanding how test and calculations factor in to accurately and reliably diagnosing disease are important considerations in this chapter.\u00a0 Being aware of public health screening efforts and better understanding disease risk and prevention efforts can help improve your life and the lives of those around us.\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n<div>\r\n<div>\r\n\r\n<a href=\"#_ftnref1\">[1]<\/a> \u201cDiagnosis-Health, United States.\u201d Centers for Disease Control and Prevention. Published June 26, 2023, Accessed July 9, 2024.\u00a0 https:\/\/www.cdc.gov\/nchs\/hus\/sources-definitions\/diagnosis.htm#:~:text=The%20act%20or%20process%20of,and%20review%20of%20laboratory%20data.\r\n\r\n<\/div>\r\n<div>\r\n\r\n<a href=\"#_ftnref2\">[2]<\/a> Institute of Medicine (US) Committee on Perinatal Transmission of HIV; National Research Council (US) and Institute of Medicine (US) Board on Children, Youth, and Families; Stoto MA, Almario DA, McCormick MC, editors. Reducing the Odds: Preventing Perinatal Transmission of HIV In The United States. Washington (DC): National Academies Press (US); 1999. 2, Public Health Screening Programs.\u00a0Available from: https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK230552\/\r\n\r\n<\/div>\r\n<div>\r\n\r\n<a href=\"#_ftnref4\">[3]<\/a> \u201cMeasurement Properties: Validity, Reliability, and Responsiveness.\u201d\u00a0 National Center for Chronic Disease Prevention and Health Promotion, Division of Population Health. Published October 31, 2018, Accessed July 15, 2024.\u00a0 <a href=\"https:\/\/archive.cdc.gov\/www_cdc_gov\/hrqol\/measurement.htm\">https:\/\/archive.cdc.gov\/www_cdc_gov\/hrqol\/measurement.htm<\/a>\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>","rendered":"<h2>Overview<\/h2>\n<p>Diagnostic tests and health screenings have a vital role to play in the surveillance of disease in patients, communities, and from a public health perspective.\u00a0 By helping to identify disease early, treatment and interventions can begin in the fight against chronic and infectious disease.<\/p>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Learning Objectives<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>By the end of this chapter, you will be able to:<\/p>\n<ul>\n<li>Know the three primary disease prevention strategies<\/li>\n<li>Differentiate between screening and diagnostic testing used to determine disease risk<\/li>\n<li>Know the types and methods of screening programs used for common causes of mortality in communities<\/li>\n<li>Understand the role of screening programs in public health<\/li>\n<li>Understand the link between disease screening and types of validity testing<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>The Three Disease Prevention Strategies<\/p>\n<p>Primary Prevention<\/p>\n<p>Primary prevention consists of measures aimed at a susceptible population or individual. The purpose of primary prevention is to prevent a disease from ever occurring. Primary prevention targets\u00a0 healthy individuals.\u00a0 Activities that limit risk exposure or increase the immunity of individuals at risk help prevent a disease from progressing .\u00a0 Examples of primary prevention include immunizations, use of condoms, abstinence education, and emergency contraception.<\/p>\n<p>Secondary Prevention<\/p>\n<p>Secondary prevention emphasizes early disease detection, and it targets\u00a0 healthy-appearing individuals with subclinical forms of the disease. The subclinical disease consists of pathologic changes but no overt symptoms that are diagnosable in a doctor&#8217;s visit. Secondary prevention often occurs in the form of screenings. For example, a Pap smear is a form of secondary prevention aimed to diagnose cervical cancer\u00a0 before progression.<\/p>\n<p>Tertiary Prevention<\/p>\n<p>Tertiary prevention targets both the clinical symptoms or screening results and outcome stages of a disease. It is implemented in patients with symptoms and aims to reduce the severity of the disease as well as any associated disease rebound. While secondary prevention seeks to prevent the onset of illness, tertiary prevention aims to reduce the effects of the disease symptoms once established in an individual.\u00a0 Tertiary prevention examples include rehabilitation efforts for cardiac concerns and strokes.<\/p>\n<p>Overview of Diagnosis<\/p>\n<p>Diagnosis is the act or process of determining or identifying the nature and cause of disease or injury through the following: evaluation of patient history, examination of the patient and review of laboratory or screening results. <a href=\"#_ftn1\">[1]<\/a><\/p>\n<p>Overview of Screenings<\/p>\n<p>Screening of disease involves using tests or procedures to identify disease or health concerns.\u00a0 Screening is most often done on individuals who are often well and do not have any observable signs or symptoms of disease.\u00a0 Most individuals getting screenings done are not aware that an illness is not detected or risk factors for disease exist.\u00a0 Often these screenings are done in combination with disease surveillance, the collection of morbidity or mortality data in a population.<\/p>\n<p>Screening is not the same as diagnosis, but some screening tests are done as diagnostic testing to identify disease or disease risk.\u00a0 Screenings are medical tests that doctors use to check for diseases and health conditions before there are any signs and symptoms.\u00a0 Screenings help find problems early, allowing opportunity for earlier and possibly easier treatment of diseases.<\/p>\n<p>Getting recommended screenings is one of the most important things you can do for. Your health.\u00a0 Depending on your age, sex, and medical history, you may need to be screened for various health diseases or conditions.\u00a0 See Table 4.4 for recommended screening exams your doctor may encourage you to consider.<\/p>\n<p>There are concerns with screening tests which include false-positive results (the wrong results) , over diagnosis of potentially benign conditions, and at times access to the tests may prove challenging for those needing the screening.\u00a0 The benefits of possible early diagnosis, early treatment, and preventive treatment outweigh the concerns some have with screenings.<\/p>\n<table>\n<tbody>\n<tr>\n<td>What Screening Tests and Results are Used for<\/td>\n<td>What Diagnostic Tests and Results are Used for<\/td>\n<\/tr>\n<tr>\n<td>To detect diseases in the early stages<\/td>\n<td>To detect the presence or absence of disease<\/td>\n<\/tr>\n<tr>\n<td>Used for asymptomatic individuals especially those with Higer risks<\/td>\n<td>Used for individuals who have symptoms to help diagnose disease or with asymptomatic individuals with a positive screening test<\/td>\n<\/tr>\n<tr>\n<td>Depending on the results the screening test would indicate a high or lower probability or risk of disease<\/td>\n<td>The result of the diagnostic test is more likely able to provide a definite disease diagnosis<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 4.1: The Main Differences Between Screening Testa and results and Diagnostic Tests and Results<\/p>\n<p>Two Types of Screenings<\/p>\n<p>Disease screening programs have a long history in strategies to control infectious disease epidemics and target chronic disease treatments.\u00a0 There are two types of screenings that help with collecting information that can help address the major causes of morbidity and mortality. These two screening efforts are mass screening and selective screening.<\/p>\n<p>Mass screenings\u00a0 are tests that are administered to total populations groups regardless of disease risk.\u00a0 Some examples of these tests include TB tests, urinalysis, drug screenings, measuring temperatures of individuals to determine possible infection risk, eye exams, pap smears and mammograms.<\/p>\n<p>Selective screenings are tests administered to high-risk population groups.\u00a0 These screening tests are used to help diagnose and detect infectious diseases, chronic diseases, and other conditions in individuals who have specific risk factors.\u00a0 These may be individuals who smoke, are obese, use IV drugs, or engage in unprotected sex or are at increased risk for adverse health concerns or outcomes.\u00a0 Regular screening of these individuals will help better diagnose and treat for possible disease concerns.<\/p>\n<p>Ensuring Screenings help with Disease Diagnosis<\/p>\n<p>For screening tests to be considered useful as well as necessary or recommended, they need to demonstrate reliability and validity.<\/p>\n<p>Reliability is the degree to which an instrument can produce consistent results and consistent results on different occasions when there is no evidence of change. This type of measurement is often about the precision of the testing. <a href=\"#_ftn4\">[3]<\/a> Validity is the degree to which an instrument measures what it is supposed to measure, and that the measurement is accurate.<\/p>\n<p>The Gold Standard with any type of screening or medical testing is the definitive diagnosis.\u00a0 This would happen when the diagnosis has been determined by surgery, biopsy, autopsy, or other testing methods.\u00a0 These tests are what are used by many health professionals for verifying, confirming and diagnosis.<\/p>\n<p>Screening measures need to be valid, reliable, and meet the gold standard for testing.\u00a0 When they are patient and health professionals can strategize treatment and care helping to limit morbidity and mortality risks.<\/p>\n<table>\n<tbody>\n<tr>\n<td>Type of Diagnostic Test<\/td>\n<td>Testing Examples<\/td>\n<\/tr>\n<tr>\n<td>Laboratory Tests<\/td>\n<td>Blood, urine sampling<\/td>\n<\/tr>\n<tr>\n<td>Imaging Tests<\/td>\n<td>CT scan, MRI, Mammography<\/td>\n<\/tr>\n<tr>\n<td>Endoscopy<\/td>\n<td>Colonoscopy, Bronchoscopy<\/td>\n<\/tr>\n<tr>\n<td>Biopsy<\/td>\n<td>Lump or node removal, tissue or cell testing<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 4.3: Four Types of Diagnostic Tests and Examples<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-57\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" srcset=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-300x232.jpg 300w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-1024x791.jpg 1024w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-768x593.jpg 768w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-1536x1187.jpg 1536w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-2048x1583.jpg 2048w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-65x50.jpg 65w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-225x174.jpg 225w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_1-350x270.jpg 350w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-58\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" srcset=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-300x232.jpg 300w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-1024x791.jpg 1024w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-768x593.jpg 768w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-1536x1187.jpg 1536w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-2048x1583.jpg 2048w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-65x50.jpg 65w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-225x174.jpg 225w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_2-350x270.jpg 350w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-59\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-300x232.jpg\" alt=\"Recommended Health screening for Adults by Age and Gender\" width=\"300\" height=\"232\" srcset=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-300x232.jpg 300w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-1024x791.jpg 1024w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-768x593.jpg 768w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-1536x1187.jpg 1536w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-2048x1583.jpg 2048w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-65x50.jpg 65w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-225x174.jpg 225w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Rcommended-Screenings-for-Adults-by-Age-and-Gender-PDF_Page_3-350x270.jpg 350w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>Table 4.4:Recommended Screening Exams\/Schedule<\/p>\n<p>Screening Calculations for Validity<\/p>\n<p>There are four measures of validity when looking at screening measures.\u00a0 Sensitivity, specificity, positive predictive value and negative predictive value.\u00a0 These four measures are described in the table below.<\/p>\n<p>When using these measures to determine if screening tests are valid, you must consider false positive and false negative results.\u00a0 False positive results may warrant unnecessary medical tests to further investigate results.\u00a0 Patients may experience anxiety because of the false positive result, only to find out that they do not have the disease.\u00a0 With false negative results, the disease is not detected in a patient who has the disease and the disease progresses.\u00a0 Being aware of these issues with screenings is important for patients to understand.<\/p>\n<table style=\"border-collapse: collapse;width: 100%\">\n<tbody>\n<tr style=\"height: 31px\">\n<td style=\"height: 31px;width: 19.9782%\">Type of Screening \u00a0Test Validity Measures<\/td>\n<td style=\"height: 31px;width: 46.6157%\">Description<\/td>\n<td style=\"width: 33.3333%\">Calculation<\/td>\n<\/tr>\n<tr style=\"height: 10px\">\n<td style=\"height: 10px;width: 19.9782%\">Sensitivity<\/td>\n<td style=\"height: 10px;width: 46.6157%\">The ability of the test to identify the presence of a disease or illness correctly; True positive and true negative results<\/td>\n<td style=\"width: 33.3333%\"><img loading=\"lazy\" decoding=\"async\" class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-8d96d4d7e14d93fff5771b5ad4a51906_l3.svg\" alt=\"\\text { Sensitivity }=\\frac{A}{A+C}\" width=\"145\" height=\"25\" \/><\/td>\n<\/tr>\n<tr style=\"height: 31px\">\n<td style=\"height: 31px;width: 19.9782%\">Specificity<\/td>\n<td style=\"height: 31px;width: 46.6157%\">The ability of a test to identify the absence of a disease or illness correctly; True negative or false positive results<\/td>\n<td style=\"width: 33.3333%\"><img loading=\"lazy\" decoding=\"async\" class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-a1020c819e936ac2388fac2debfefad4_l3.svg\" alt=\"\\text { Specificity }=\\frac{D}{B+D}\" width=\"145\" height=\"24\" \/><\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 19.9782%\">Positive Predictive Values (PPV)<\/td>\n<td style=\"height: 15px;width: 46.6157%\">The likelihood a person who has a positive test result does have the disease or illness<\/td>\n<td class=\"column-3\" style=\"width: 33.3333%\"><img loading=\"lazy\" decoding=\"async\" class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-c097c212a2f527e70e566942f6e21823_l3.svg\" alt=\"\\text { Predictive value positive }=\\frac{A}{A+B}\" width=\"254\" height=\"25\" \/><\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 19.9782%\">Negative Predictive Value (NPV)<\/td>\n<td style=\"height: 15px;width: 46.6157%\">The likelihood a person who has a negative test result indeed does not have the disease or illness<\/td>\n<td class=\"column-3\" style=\"width: 33.3333%\"><img loading=\"lazy\" decoding=\"async\" class=\"ql-img-inline-formula quicklatex-auto-format\" title=\"Rendered by QuickLaTeX.com\" src=\"https:\/\/pressbooks.lib.vt.edu\/app\/uploads\/quicklatex\/quicklatex.com-f172127158c952941aba24da89ba881a_l3.svg\" alt=\"\\text { Predictive value negative }=\\frac{D}{C+D}\" width=\"259\" height=\"24\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 4.5 The Four Measures of Screening Test Validity<\/p>\n<p>The presentation of diagnostic exam results is often in 2&#215;2 tables, such as Table 4.6.\u00a0 The values within this table can help to determine sensitivity and specificity, as well as other epidemiologic value data.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-77 size-medium\" src=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-300x88.jpeg\" alt=\"Diagnostic testing 2x2 accuracy table\" width=\"300\" height=\"88\" srcset=\"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-300x88.jpeg 300w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-768x224.jpeg 768w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-65x19.jpeg 65w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-225x66.jpeg 225w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1-350x102.jpeg 350w, https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-content\/uploads\/sites\/321\/2024\/08\/Diagnostic__Testing__Accuracy__Table__1.jpeg 794w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>Table 4.6 Diagnostic Testing 2&#215;2 Accuracy Table<\/p>\n<p>Sensitivity and Specificity Testing<\/p>\n<p>In epidiemiology, sensitivity and specificity are mathematical calculations used to describe the accuracy of a test that reports the presence or absence of a disease or medical condition.<\/p>\n<p>If individuals who have a disease or medical condition are identified as &#8220;positive&#8221; and those who are not are identified as &#8220;negative&#8221; , then sensitivity is a measure of how well the test can identify the positives and specificity is a measure of how well a test can measure the\u00a0 negatives.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"_O8OzZpmONIOV5OMPvtC-2Ag_65\" class=\"bCOlv\" data-ved=\"2ahUKEwjZl6Cux-OHAxWDCnkGHT6oD4sQkLgIKAZ6BAgoEBA\">\n<div class=\"IZE3Td\">\n<div data-ved=\"2ahUKEwjZl6Cux-OHAxWDCnkGHT6oD4sQoPIHegQIKBAR\">\n<div class=\"PZPZlf\" data-attrid=\"lab\/content\/Sensitivity\">\n<div id=\"O8OzZpmONIOV5OMPvtC-2Ag__68\">\n<div class=\"wDYxhc NFQFxe viOShc LKPcQc\" data-md=\"471\">\n<div class=\"V3FYCf\">\n<div class=\"wDYxhc\" data-md=\"61\">\n<div class=\"LGOjhe\" role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\"><span class=\"BxUVEf ILfuVd\" lang=\"en\"><span class=\"hgKElc\">Sensitivity is the percentage of people with the disease who are correctly identified by the test. Specificity is the percentage of people without the disease who are correctly excluded by the test. These concepts have clinical importance\u00a0 in helping to\u00a0 confirm or exclude disease during screening.<\/span><\/span><\/div>\n<\/div>\n<\/div>\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">In medical screening and diagnosis, test sensitivity is the ability of a test to correctly identify individuals with disease ( true positives), where test specificity is the ability of a test to correctly identify those who do not have disease ( true negatives).<\/div>\n<\/div>\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Examples of Test Sensitivity and Specificity<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>If 100 individuals who were screened have a disease and 53 test positive, then the test has a 53% sensitivity.\u00a0 If 100 individuals with no disease are screened and 92 return a negative result, then the test has a 92% specificity.<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<div class=\"wDYxhc NFQFxe viOShc LKPcQc\" data-md=\"471\">\n<div class=\"V3FYCf\">\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\">A test which accurately and reliably detects the presence of a disease or a medical condition resulting in a high number of true positives and a low number of true negatives has a high sensitivity.\u00a0 A test that excludes individuals who do not have the disease or medical condition, resulting in a high number or true negatives and a low number of false positives, will have a high specificity.<\/div>\n<\/div>\n<\/div>\n<div role=\"heading\" data-attrid=\"wa:\/description\" data-hveid=\"CGIQAA\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example: Hepatitis A Blood Test for Sensitivity and Specificity in a Population<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>A healthcare provider uses a blood test to determine whether or not individuals have Hepatitis A:<\/p>\n<ul>\n<li style=\"list-style-type: none\">\n<ul>\n<li class=\"half_rhythm\">\n<div>A total of 1,000 individuals had their blood tested for Hepatitis A.<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>427 individuals had positive findings, and 573 individuals had negative findings.<\/div>\n<\/li>\n<li class=\"half_rhythm\">Out of the 427 individuals who had positive findings, 369 of them had the disease.<\/li>\n<li>Out of the 573 individuals who had negative findings, 558 did not have the disease.<\/li>\n<li class=\"half_rhythm\">The healthcare provider found that a total of 384 individuals actually had the disease,<\/li>\n<li class=\"half_rhythm\">So how accurate was the Hepatitis A blood test in the 1000 individuals?<\/li>\n<\/ul>\n<\/li>\n<li>Using the 2X2 table approach to sort this data, the following chart:<\/li>\n<\/ul>\n<table style=\"border-collapse: collapse;width: 100%;height: 60px\">\n<tbody>\n<tr style=\"height: 15px\">\n<td style=\"width: 25%;height: 15px\">Blood Test Results<\/td>\n<td style=\"width: 25%;height: 15px\">Hepatitis A Present<\/td>\n<td style=\"width: 25%;height: 15px\">Hepatitis A Not Present<\/td>\n<td style=\"width: 25%;height: 15px\">Total<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 25%;height: 15px\">Positive<\/td>\n<td style=\"width: 25%;height: 15px\">369(A)<\/td>\n<td style=\"width: 25%;height: 15px\">58(B)<\/td>\n<td style=\"width: 25%;height: 15px\">427<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 25%;height: 15px\">Negative<\/td>\n<td style=\"width: 25%;height: 15px\">15(C)<\/td>\n<td style=\"width: 25%;height: 15px\">558(D)<\/td>\n<td style=\"width: 25%;height: 15px\">573<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 25%;height: 15px\">Total<\/td>\n<td style=\"width: 25%;height: 15px\">384(A+C)<\/td>\n<td style=\"width: 25%;height: 15px\">616(B+D)<\/td>\n<td style=\"width: 25%;height: 15px\">1000<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<ul>\n<li>Calculation Results for Sensitivity and Specificity:<\/li>\n<\/ul>\n<p><i>Sensitivity<\/i><\/p>\n<ul>\n<li class=\"half_rhythm\">\n<div>Sensitivity=(True Positives (A))\/(True Positives (A)+False Negatives (C))<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Sensitivity=(369 (A))\/(369(A)+15 (C))<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Sensitivity=369\/384<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Sensitivity=0.961 or 96.1%<\/div>\n<\/li>\n<\/ul>\n<p><i>Specificity<\/i><\/p>\n<ul>\n<li class=\"half_rhythm\">\n<div>Specificity=(True Negatives (D))\/(True Negatives (D)+False Positives (B))<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Specificity=(558\u00a0(D))\/(558(D)+58 (B))<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Specificity=558\/616<\/div>\n<\/li>\n<li class=\"half_rhythm\">\n<div>Specificity=0.906 or 90.6%<\/div>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Community and Public Health Benefits of Screening Programs<\/p>\n<p>Disease screening programs have a long history in strategies to control infectious disease epidemics and target chronic disease treatments. <a href=\"#_ftn2\">[2]<\/a> Goals of public health screening programs need to be clearly specified and shown to impact case findings.<\/p>\n<p>Understanding the natural history of the disease, knowing what interventions and treatments the scientific and medical community believe work for individuals determined to have disease and finding or having evidence that early intervention improves outcomes are all important considerations for a well-organized public health screening effort.<\/p>\n<p>Screening programs should measure conditions that can control possible epidemics of infectious disease and target treatment for chronic diseases.\u00a0 Understanding the tangible public health benefits of screening efforts boost confidence that the health care system is working and that all patients have been treated fairly and if needed will benefit from treatment that should be made accessible to them.<\/p>\n<table style=\"border-collapse: collapse;width: 100%\">\n<tbody>\n<tr>\n<td style=\"width: 100%\">Tangible Public Health Benefits of Screening Programs<\/p>\n<ol>\n<li>Help control epidemics of infectious disease<\/li>\n<li>Target treatment for chronic disease<\/li>\n<li>Early diagnosis and better management of chronic diseases<\/li>\n<li>Improve health and quality of life of populations and communities<\/li>\n<\/ol>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Table 4.2: Tangible Public Health Benefits of Screening Programs<\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">The WHO, World Health Organization, states that screening programs should be done only for diseases with serious consequences, screening programs should have clear benefits to people\u2019s health, and screenings should be reliable and not harmful.\u00a0 It is also critical that effective treatments for disease identified in early stages during screening have clear evidence that the treatment is more effective when started before symptoms arise like with Breast Cancer. The public should always have information available to them on screening options and make informed decisions on whether they want to have the screening test. [<\/span><a style=\"text-align: initial;font-size: 1em\" href=\"#_ftn3\">3]<\/a><\/p>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Key Takeaways<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>In this chapter you learned about disease prevention strategies, screenings for disease, and diagnostic tests to confirm chronic and infectious diseases.\u00a0 Screening calculations, validity and understanding how test and calculations factor in to accurately and reliably diagnosing disease are important considerations in this chapter.\u00a0 Being aware of public health screening efforts and better understanding disease risk and prevention efforts can help improve your life and the lives of those around us.<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div>\n<div>\n<p><a href=\"#_ftnref1\">[1]<\/a> \u201cDiagnosis-Health, United States.\u201d Centers for Disease Control and Prevention. Published June 26, 2023, Accessed July 9, 2024.\u00a0 https:\/\/www.cdc.gov\/nchs\/hus\/sources-definitions\/diagnosis.htm#:~:text=The%20act%20or%20process%20of,and%20review%20of%20laboratory%20data.<\/p>\n<\/div>\n<div>\n<p><a href=\"#_ftnref2\">[2]<\/a> Institute of Medicine (US) Committee on Perinatal Transmission of HIV; National Research Council (US) and Institute of Medicine (US) Board on Children, Youth, and Families; Stoto MA, Almario DA, McCormick MC, editors. Reducing the Odds: Preventing Perinatal Transmission of HIV In The United States. Washington (DC): National Academies Press (US); 1999. 2, Public Health Screening Programs.\u00a0Available from: https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK230552\/<\/p>\n<\/div>\n<div>\n<p><a href=\"#_ftnref4\">[3]<\/a> \u201cMeasurement Properties: Validity, Reliability, and Responsiveness.\u201d\u00a0 National Center for Chronic Disease Prevention and Health Promotion, Division of Population Health. Published October 31, 2018, Accessed July 15, 2024.\u00a0 <a href=\"https:\/\/archive.cdc.gov\/www_cdc_gov\/hrqol\/measurement.htm\">https:\/\/archive.cdc.gov\/www_cdc_gov\/hrqol\/measurement.htm<\/a><\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n","protected":false},"author":345,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"Screening and Diagnostic Tests","pb_subtitle":"Screening and Diagnostic Tests","pb_authors":["bazan3"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[60],"license":[53],"class_list":["post-29","chapter","type-chapter","status-publish","hentry","contributor-bazan3","license-cc-by"],"part":3,"_links":{"self":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapters\/29","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/wp\/v2\/users\/345"}],"version-history":[{"count":20,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapters\/29\/revisions"}],"predecessor-version":[{"id":140,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapters\/29\/revisions\/140"}],"part":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapters\/29\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/wp\/v2\/media?parent=29"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/pressbooks\/v2\/chapter-type?post=29"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/wp\/v2\/contributor?post=29"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pb-sandbox.library.illinois.edu\/introductiontoepidemiology\/wp-json\/wp\/v2\/license?post=29"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}