Presentation on theme: "Module 4: Screening Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School."— Presentation transcript:
1 Module 4: ScreeningDeveloped through the APTR Initiative to Enhance Prevention and PopulationHealth Education in collaboration with the Brody School of Medicine at East Carolina University with funding from the Centers for Disease Control and Prevention
2 AcknowledgmentsAPTR wishes to acknowledge the following individuals that developed this module:Anna Zendell, PhD, MSWCenter for Public Health Continuing EducationUniversity at Albany School of Public HealthJoseph Nicholas, MD, MPHUniversity of Rochester School of MedicineMary Applegate, MD, MPHCheryl Reeves, MS, MLSThis education module is made possible through the Centers for Disease Control and Prevention (CDC) and the Association for Prevention Teaching and Research (APTR) Cooperative Agreement, No. 5U50CD The module represents the opinions of the author(s) and does not necessarily represent the views of the Centers for Disease Control and Prevention or the Association for Prevention Teaching and Research.
3 Presentation Objectives Define screening and identify appropriate conditions for screeningEvaluate screening tests in terms of their validity, results and generalizabilityEvaluate the effectiveness of a screening program and discuss the common biasesDiscuss ethical considerations in screening
5 Oprah’s Full Body ScanAs you watch this clip and complete the module, think about the implications for patient screening based on this technologyMedical concerns?Ethical considerations?Access issues?Informed decision-making after screening?
6 Preventive Medicine & Public Health Share common goalsEnhance quality of life of patientsHealth promotionDisease and injury preventionPreventive medicine promotes these goals at the individual and population levels, while public health focuses on populations.
8 Screening DefinedPresumptive identification of an unrecognized disease through tests, examinations, or other procedures which can be applied rapidlyScreening tests sort out apparently well persons who probably have a disease from those who probably do not.
9 Importance of Screening Early detectionLeads to early treatmentCan lead to a decrease in morbidity and mortalityCan break the chain of transmission and development of new casesIs often cost-effectiveThe human body is continually changingJekel et al:, 1996; McKenzie et al:, 2008; Londrigan & Lewenson: 2011
10 Screening-Diagnosis Connection Screening starts before diagnosisHistory questionsPhysical exam findingsLab testsPre-test probabilityResults of screening trigger diagnostic work-up and preventive interventionsJekel et al:, 1996; McKenzie et al:, 2008
11 Screening versus Diagnostic Tests ≠Screening TestDiagnostic Test
12 Screening versus Diagnostic Tests ≠Screening TestDiagnostic TestIdentifies asymptomatic people who may have a disease
13 Screening versus Diagnostic Tests ≠Screening TestDiagnostic TestIdentifies asymptomatic people who may have a diseaseDetermines presence or absence of disease when patient shows signs or symptoms
14 Characteristics of a Good Screening Test SimpleRapidInexpensiveSafeAvailableAcceptable
16 Common Disease Screenings Pap smear screens for ___________________________Fasting blood sugar screens for _________________Fecal occult blood test screens for ______________Blood pressure screens for ______________________Bone densitometry screens for _________________PSA test screens for _____________________________PPD test screens for _____________________________Mammography screens for ______________________USPSTF: 2009
17 Common Disease Screenings Pap smear screens for cervical cancerFasting blood sugar screens for diabetesFecal occult blood test screens for colorectal cancerBlood pressure screens for hypertensionBone densitometry screens for osteoporosis & osteopeniaPSA test screens for prostate cancerPPD test screens for tuberculosisMammography screens for breast cancer.USPSTF: 2009
18 Common Wellness Screenings ObesityDental caries, oral cancerDrugs, Alcohol, and TobaccoWeight, Body Mass IndexOral examinationUrine test, NMASSIST, or Flagerstrom Tolerance Test for Nicotine Dependency
19 Breast Cancer Screening Standard practiceAnnual mammograms for women age 40+ yearsStart earlier if family history of breast cancer2009 US Preventive Services Task Force (USPSTF) recommendationsMammograms not universal for women age yearsBi-annual mammograms for women 50+ yearsCost-benefit analysisFalse positivesUnnecessary invasive procedures
20 Colon Cancer Screening Multiple screening optionsColonoscopy – gold standardSigmoidoscopyVirtual colonoscopy – CT colonoscopyBarium enemaFecal testing – occult blood, DNA testRecommended age, frequency vary by test and family history
21 Case Study Colorectal Cancer Screening Practice evaluation of diagnostic test characteristics and screening programsDiscuss prevention conceptsApply this at patient andpopulation level
22 Newborn ScreeningMandatory universal screen for disorders, including metabolic, hormonal, hematologic, and infectious conditionsStates vary in what diseases they test forHeel prick blood test hours post birth - if done too early, metabolic disease may not show up in bloodFamily history may indicate need for additional screensNewborn health screening—mandatory screen for disorders, such as metabolic, hormonal, blood, and infectious conditions.States vary in what diseases test forFor example, NY tests for over 40 conditions, including HIV.Heel prick blood test done hours post birthMost states now use a tandem mass spectrometer to test blood; tests many metabolic conditions with one drop of blood.If done too early, presence of diseases may not show up in the blood.Some common screens include: PKU, Galactosemia, MCAD, sickle cell anemia, HIV.In addition to mandated tests, family hx or ethnicity may indicate need for additional screens.Non-mandatory screens not paid for by state, and may/may not be covered under personal health insurance.
24 Evaluating TestsReliability and validity are central concepts in evaluating testsDistinction between reliability and validityReliability: consistency of test at different times or under differing conditionsValidity: how well test distinguishes between who has disease and who does notFortune & Reid: 1998; Jekel et al:, 1996
25 Characteristics of a Screening Test VALIDITY and RELIABILITYFortune & Reid: 1998
26 Reliability Also known as consistency Ability to yield the same results with repeated measurements of same constructDegree to which results are free from random errorJekel: 1996; Al-Eisa: 2009
27 Common Types of Reliability Intra-subjectJekel: 1996; Al-Eisa: 2009
28 Common Types of Reliability Intra-raterIntra-subjectJekel: 1996; Al-Eisa: 2009
29 Common Types of Reliability Intra-raterIntra-subjectInter-raterJekel: 1996; Al-Eisa: 2009
30 Common Types of Reliability Intra-raterIntra-subjectInter-raterInstrumentJekel: 1996; Al-Eisa: 2009
31 Sensitivity Measures validity of screening tests Ability to identify those with disease correctlyMinimizes false negatives – if test highly sensitiveSNOUT – Sensitive test with Negative result rules OUT disease
32 Specificity Ability to identify those without disease correctly Minimizes false positives – if test highly specificSPIN – Specific test with Positive result rules IN disease
33 Relationship Between Sensitivity and Specificity PSA levelSensitivitySpecificity1.0100212.0483.0604.099735.096766.094797.090838.0889.06810.0549311.04712.0309513.02314.0179715.011Morgan TO et al; NEJM, 1996
37 Predictive ValuesPositive predictive valueNegative predictive value
38 Positive Predictive Value (PPV) NOT inherent characteristic of a screening testPercent of positive tests that are truly positiveIf test result is positive, what is probability that the patient has the disease?Is affected by several factorsSpecificity & specificity of the screening testPrevalence of disease
39 Negative Predictive Value (NPV) NOT inherent characteristic of a screening testPercent of negative tests that are truly negativeIf test result is negative, what is the probability that patient does not have the disease?
40 Test Characteristics and Population Tested Sensitivity and specificity are constant for a particular testPPV and NPV vary dramatically, depending on prevalence of target condition in population testedLow prevalence low PPV, high NPVHigh prevalence high PPV, low NPV
41 Predictive Value and Prevalence (in test with 98% sensitivity, 92% specificity)
43 1,000 people at Prenatal Clinic Positive Predictive Value Low PrevalenceHIV Status1,000 people at Prenatal ClinicHIV-Positive (15)HIV-Negative (985)1.5% PrevalenceELISA ResultPositiveTrue Positive (14)False Positive (99)14= 12.4% PPVNegativeFalse Negative (1)True Negative (886)886= 99.9% NPVSensitivity (95%)Specificity (90%)
44 Positive Predictive Value High Prevalence HIV Status1,000 people at STD ClinicHIV-Positive (60)HIV-Negative (940)6% PrevalenceELISA ResultPositiveTrue Positive (57)False Positive (94)57= 37.75% PPVNegativeFalse Negative (3)True Negative (846)846= 99.6% NPVSensitivity (95%)Specificity (90%)
45 Positive Predictive Value Very High Prevalence HIV Status1,000 people at Clinic in ZambiaHIV-Positive (240)HIV-Negative (760)24% PrevalenceELISA ResultPositiveTrue Positive (228)False Positive (76)228= 75% PPVNegativeFalse Negative (12)True Negative (684)684= 98.3% NPVSensitivity (95%)Specificity (90%)
46 Multiple Screening Tests Simultaneous Use of different tests concurrently to screen for same conditionExample: Prenatal multiple marker screening for Down SyndromeMeasures levels of 3 biomarkers in mother’s blood:AFP: alpha-fetoprotein, protein produced by fetushCG: human chorionic gonadotropin, hormone produced by placentaEstriol: a hormone produced by both fetus and placentaResults of ALL 3 tests increases sensitivity and specificity
47 Multiple Screening Tests Sequential Use of two-stage screening to target testing effortsExample: Early pregnancy gestational diabetes screeningFirst trimester risk assessment—identifies women at higher risk of gestational diabetesOral Glucose Tolerance Test (OGTT) right away for those whose first screen indicates high risk
48 Multiple Screening Tests Sequential Two-stage screening to maximize predictive valueExample: HIV screening in suburban primary care officeRisk assessment questionnaire about sexual and drug use historyHIV blood test for all patients whose questionnaire indicates risk factors for HIV infection
50 Screening Effectiveness Evaluation Test characteristics (sensitivity & specificity) alone are never sufficient for a sound decision about whether to use a screening testOther screening considerationsBenefits vs. risksPrevalence of target conditionInconvenienceCosts/resource expendituresPatient values and cultural normsGuyatt: 2009
51 Study Design Testing a Test Assessing a screening/diagnostic testProperties & accuracyComparison of test to “gold standard”Most definitive diagnostic procedure or best available laboratory testNot always a gold standard for a procedureUSPSTF recommended
53 USPSTF ActivitiesSystematically reviews the evidence of effectiveness and develops recommendations for clinical preventive servicesRecommendations include:Screening testsCounselingPreventive medicationsCourtesy of Diana Pettiti, USPSTF: 2010
54 USPSTF Methodology Define analytic framework – outcomes & questions Define and retrieve relevant evidenceEvaluate QUALITY of studies (good, fair, poor)Synthesize and judge STRENGTH of overall evidence (convincing, adequate, inadequate)Determine BALANCE of benefits and harms Benefits – Harms = Net BenefitLink recommendation to judgment about net benefits: Grades: A, B, C, D, I (inadequate evidence)Courtesy of Diana Pettiti, USPSTF: 2010
55 Critical Appraisal Questions Do the studies have the appropriate research design to answer key questions?Are the existing studies high quality?Are the results of the studies applicable to the general US primary care population and setting?Courtesy of Diana Pettiti, USPSTF: 2010
56 Critical Appraisal Questions How many relevant studies have been done?How large are the studies?How consistent are the results of the studies?Are there other factors that help us assess the certainty of the evidence? (e.g. dose-response effects, biologic plausibility)Courtesy of Diana Pettiti, USPSTF: 2010
57 Linking Recommendations to Benefits: USPSTF Recommendations Certainty of Net BenefitMagnitude of Net BenefitSubstantialModerateSmallZero/negativeHighABCDLowInsufficient (I Statement)Courtesy of Diana Pettiti, USPSTF: 201057
58 Communicating USPSTF Recommendations GradeGrade DefinitionSuggestion for PracticeAUSPSTF recommends the service.There is high certainty that the net benefit is substantial.Offer or provide this service.BThe USPSTF recommends the service.There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.CUSPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient.There is moderate or high certainty that the net benefit is small.Offer or provide this service only if there are other considerations in support of the offering or providing the service in an individual patient.DUSPSTF recommends against the service.There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.Discourage the use of this service.IUSPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service.Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined.Read “Clinical Considerations” section of USPSTF Recommendation Statement. If offered the service, patients should understand the uncertainty about the balance of benefits and harms.Courtesy of Diana Pettiti, USPSTF: 2010
59 Comparison of Screening Tools Newer tests vs. gold standardBest tests for your populationValidity in your populationAccessibilityCostCapacity of local health care systemNeed a system in place to be able to screen AND to deal with positive results
60 Testing a Test Cervical Cancer NO Cervical Cancer Patients without Liquid-basedPap smear –the NEW testNOCervical CancerPatients withoutevidence ofcervical cancerCervical CancerStandardPap smear –the GOLDSTANDARDNOCervical Cancer
61 Evaluating Screening Research Are study methodology and results credible?Have sensitivity, specificity and predictive values been calculated and reported?Is the population tested similar to my patient population?How can I use these results in a screening program or patient care?Does this screening improve the present state of medical screening?
62 Screening Outcome Considerations Long-term Outcomes Lead time bias: over-estimation of survival rate among screening-detected casesWhen survival is calculated from diagnosis pointLength bias: over-estimation of survival rate among screening-detected casesDue to excess of slowly progressing cases among those identified by screeningKoretz: 2009
63 To Screen or Not to Screen Essential Criteria DiseaseTestTreatmentCostProgrammingCondition should be important health problem.Test must be simple, safe, precise, valid.Must be evidence of effective treatment and that early treatment will lead to better outcomes.Evidence on cost- effectiveness of screening for interventions and outcomes.Evidence from randomized controlled trials that program effective in reducing mortality and morbidity.Epidemiology of disease must be understood.Must be acceptable to population and health providers giving test.Benefits outweigh physical and psychological harms if any.Criteria/protocol on next steps for positive tests.Protocols for implementation and evaluation of screening program.
64 PseudodiseaseDefinition: Identifying a disease that is unlikely to impact patient over lifetimeProstate or breast cancer may be present in bodyMay never become clinically apparentIdentifying pseudodisease is nearly impossible until person dies from unrelated causesGold standard tests cannot predict future trajectory of a conditionDurgin: 2005
66 Ethical Considerations Mandated screeningGenetic testingDisparitiesCreation of screening program
67 Mandatory Screening Newborn screening Syphilis testing for marriage licensesTB screening for health care workersDrug testing for airline pilots
68 Mandatory Screening Need to assess costs vs. benefits at all levels IndividualSocietalHealthcare system
69 Mandatory Screening Pros Cons Identify serious problems that could harm others OR where immediate treatment is imperativeConsPotential harm to patient autonomyConfidentiality concernsTesting low risk population reduces PPVConsequences of false positive tests
70 Genetics Testing Benefits Learn if individual carries a gene for a disease and might pass it on to childrenScreen unborn fetus for diseaseTest for genetic diseases in children or adults before symptoms emerge
71 Genetic Testing Concerns Results difficult to interpret; not always clear cutEmployment issuesHealth/life insurance consequencesAdded stressCostsConfidentialityOwnership of DNAKalb, 2006
72 Disparities Access to Screening Geographic regionRuralInner cityUninsured and underinsuredScreening and follow-up testing/treatmentCost-prohibitive without health insuranceMinority and immigrant populationsLack of culturally competent healthcare providersLow health literacy
73 Disparities CulturalCross-cultural differences in health literacy and attitudesCulturally relevant screeningScreening practices may need to be adapted
74 Developing a Screening Program Ethical Considerations How ethical is it to:Use a test that may tell people they have condition when they do not?Use a test that may tell people they do not have condition when they actually do?Use a test if there is no system in place to treat those who test positive?Truglio et al: 2011
75 Implications for Practice Strategic targeting for screeningGroups with higher prevalence – increase PPVProvider vs. patient – who is more likely to request?Growing body of evidence-based medicine allows us to:Identify more precise screening protocolsWeigh benefits/drawbacks of screening testStrategic screening can be cost-effective
76 Summary Screening is bedrock of secondary prevention Screening and diagnosis are not the sameSensitivity and specificity are characteristics of a screening test that determine a test’s validityPredictive values are affected by sensitivity & specificity of test and by prevalence of the diseaseScreening of high-risk populations increases positive predictive valueScreening decisions must weigh acceptability and applicability to practitioner, population, and individual
77 Collaborating Institutions Department of Public HealthBrody School of Medicine at East Carolina UniversityDepartment of Community & Family MedicineDuke University School of Medicine
Your consent to our cookies if you continue to use this website.