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Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School of Medicine at East.

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Presentation on theme: "Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School of Medicine at East."— Presentation transcript:

1 Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School of Medicine at East Carolina University with funding from the Centers for Disease Control and Prevention

2 APTR wishes to acknowledge the following individuals that developed this module: Anna Zendell, PhD, MSW Center for Public Health Continuing Education University at Albany School of Public Health Joseph Nicholas, MD, MPH University of Rochester School of Medicine Mary Applegate, MD, MPH University at Albany School of Public Health Cheryl Reeves, MS, MLS Center for Public Health Continuing Education University at Albany School of Public Health This 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 1. Define screening and identify appropriate conditions for screening 2. Evaluate screening tests in terms of their validity, results and generalizability 3. Evaluate the effectiveness of a screening program and discuss the common biases 4. Discuss ethical considerations in screening

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5 As you watch this clip and complete the module, think about the implications for patient screening based on this technology Medical concerns? Ethical considerations? Access issues? Informed decision-making after screening?

6 Share common goals Enhance quality of life of patients Health promotion Disease and injury prevention Preventive medicine promotes these goals at the individual and population levels, while public health focuses on populations.

7 Primary Prevention Secondary Prevention Tertiary Prevention McKenzie et al.: 2008

8 Presumptive identification of an unrecognized disease through tests, examinations, or other procedures which can be applied rapidly Screening tests sort out apparently well persons who probably have a disease from those who probably do not.

9 Early detection Leads to early treatment Can lead to a decrease in morbidity and mortality Can break the chain of transmission and development of new cases Is often cost-effective The human body is continually changing Jekel et al:, 1996; McKenzie et al:, 2008; Londrigan & Lewenson: 2011

10 Screening starts before diagnosis History questions Physical exam findings Lab tests Pre-test probability Results of screening trigger diagnostic work-up and preventive interventions Jekel et al:, 1996; McKenzie et al:, 2008

11 Diagnostic Test Screening Test

12 Diagnostic Test Screening Test Identifies asymptomatic people who may have a disease

13 Screening Test Identifies asymptomatic people who may have a disease Diagnostic Test Determines presence or absence of disease when patient shows signs or symptoms

14 Simple Rapid Inexpensive Safe Available Acceptable

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16 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 Pap smear screens for cervical cancer Fasting blood sugar screens for diabetes Fecal occult blood test screens for colorectal cancer Blood pressure screens for hypertension Bone densitometry screens for osteoporosis & osteopenia PSA test screens for prostate cancer PPD test screens for tuberculosis Mammography screens for breast cancer. USPSTF: 2009

18 Obesity Dental caries, oral cancer Drugs, Alcohol, and Tobacco Weight, Body Mass Index Oral examination Urine test, NMASSIST, or Flagerstrom Tolerance Test for Nicotine Dependency

19 Standard practice Annual mammograms for women age 40+ years Start earlier if family history of breast cancer 2009 US Preventive Services Task Force (USPSTF) recommendations Mammograms not universal for women age years Bi-annual mammograms for women 50+ years Cost-benefit analysis False positives Unnecessary invasive procedures

20 Multiple screening options Colonoscopy – gold standard Sigmoidoscopy Virtual colonoscopy – CT colonoscopy Barium enema Fecal testing – occult blood, DNA test Recommended age, frequency vary by test and family history

21 Practice evaluation of diagnostic test characteristics and screening programs Discuss prevention concepts Apply this at patient and population level

22 Mandatory universal screen for disorders, including metabolic, hormonal, hematologic, and infectious conditions States vary in what diseases they test for Heel prick blood test hours post birth - if done too early, metabolic disease may not show up in blood Family history may indicate need for additional screens

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24 Reliability and validity are central concepts in evaluating tests Distinction between reliability and validity Reliability: consistency of test at different times or under differing conditions Validity: how well test distinguishes between who has disease and who does not Fortune & Reid: 1998; Jekel et al:, 1996

25 VALIDITY and RELIABILITY Fortune & Reid: 1998

26 Also known as consistency Ability to yield the same results with repeated measurements of same construct Degree to which results are free from random error Jekel: 1996; Al-Eisa: 2009

27 Intra-subject

28 Intra-rater Jekel: 1996; Al-Eisa: 2009

29 Intra-subject Inter-rater Intra-rater Jekel: 1996; Al-Eisa: 2009

30 Intra-subject Instrument Inter-rater Intra-rater Jekel: 1996; Al-Eisa: 2009

31 Measures validity of screening tests Ability to identify those with disease correctly Minimizes false negatives – if test highly sensitive SNOUT – Sensitive test with Negative result rules OUT disease

32 Ability to identify those without disease correctly Minimizes false positives – if test highly specific SPIN – Specific test with Positive result rules IN disease

33 PSA levelSensitivitySpecificity Morgan TO et al; NEJM, 1996

34 True Positive Disease PresentDisease Absent Test + Test - False Positive False Negative True Negative

35 Sensitivity= True positiveFalse positive False negativeTrue negative Present Absent DISEASE Test + Test - True positives True positives + false negatives Sensitivity

36 Specificity True positiveFalse positive False negativeTrue negative Present Absent DISEASE Test + Test - = Specificity True negatives True negatives + false positives

37 Positive predictive value Negative predictive value

38 NOT inherent characteristic of a screening test Percent of positive tests that are truly positive If test result is positive, what is probability that the patient has the disease? Is affected by several factors Specificity & specificity of the screening test Prevalence of disease

39 NOT inherent characteristic of a screening test Percent of negative tests that are truly negative If test result is negative, what is the probability that patient does not have the disease?

40 Sensitivity and specificity are constant for a particular test PPV and NPV vary dramatically, depending on prevalence of target condition in population tested Low prevalence low PPV, high NPV High prevalence high PPV, low NPV

41 Prevalence Predictive Value

42 Disease DiseasedNon-Diseased PVs Test Result PositiveTrue Positive (TP) False Positive (FP) (Type 1 error) TP TP + FP Negative False Negative (FN) (Type II error) True Negative (TN) TN TN +FN Sensitivity TP TP + FN Specificity TN TN + FP

43 HIV Status 1,000 people at Prenatal Clinic HIV-Positive (15)HIV-Negative (985)1.5% Prevalence ELISA Result PositiveTrue Positive (14)False Positive (99) = 12.4% PPV NegativeFalse Negative (1)True Negative (886) = 99.9% NPV Sensitivity (95%)Specificity (90%)

44 HIV Status 1,000 people at STD Clinic HIV-Positive (60)HIV-Negative (940)6% Prevalence ELISA Result PositiveTrue Positive (57)False Positive (94) = 37.75% PPV NegativeFalse Negative (3)True Negative (846) = 99.6% NPV Sensitivity (95%)Specificity (90%)

45 HIV Status 1,000 people at Clinic in Zambia HIV-Positive (240)HIV-Negative (760)24% Prevalence ELISA Result PositiveTrue Positive (228)False Positive (76) = 75% PPV NegativeFalse Negative (12)True Negative (684) = 98.3% NPV Sensitivity (95%)Specificity (90%)

46 Use of different tests concurrently to screen for same condition Example: Prenatal multiple marker screening for Down Syndrome Measures levels of 3 biomarkers in mothers blood: AFP: alpha-fetoprotein, protein produced by fetus hCG: human chorionic gonadotropin, hormone produced by placenta Estriol: a hormone produced by both fetus and placenta Results of ALL 3 tests increases sensitivity and specificity

47 Use of two-stage screening to target testing efforts Example: Early pregnancy gestational diabetes screening First trimester risk assessmentidentifies women at higher risk of gestational diabetes Oral Glucose Tolerance Test (OGTT) right away for those whose first screen indicates high risk

48 Two-stage screening to maximize predictive value Example: HIV screening in suburban primary care office Risk assessment questionnaire about sexual and drug use history HIV blood test for all patients whose questionnaire indicates risk factors for HIV infection

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50 Test characteristics (sensitivity & specificity) alone are never sufficient for a sound decision about whether to use a screening test Other screening considerations Benefits vs. risks Prevalence of target condition Inconvenience Costs/resource expenditures Patient values and cultural norms Guyatt: 2009

51 Assessing a screening/diagnostic test Properties & accuracy Comparison of test to gold standard Most definitive diagnostic procedure or best available laboratory test Not always a gold standard for a procedure USPSTF recommended

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53 Systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services Recommendations include: Screening tests Counseling Preventive medications Courtesy of Diana Pettiti, USPSTF: 2010

54 1. Define analytic framework – outcomes & questions 2. Define and retrieve relevant evidence 3. Evaluate QUALITY of studies (good, fair, poor) 4. Synthesize and judge STRENGTH of overall evidence (convincing, adequate, inadequate) 5. Determine BALANCE of benefits and harms Benefits – Harms = Net Benefit 6. Link recommendation to judgment about net benefits: Grades: A, B, C, D, I (inadequate evidence) Courtesy of Diana Pettiti, USPSTF: 2010

55 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 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 Certainty of Net Benefit Magnitude of Net Benefit SubstantialModerateSmallZero/negative High ABCD Moderate BBCD Low Insufficient (I Statement) Courtesy of Diana Pettiti, USPSTF: 2010

58 Grade Grade Definition Suggestion for Practice A USPSTF recommends the service. There is high certainty that the net benefit is substantial. Offer or provide this service. B The 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. Offer or provide this service. C USPSTF 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. D USPSTF 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. I USPSTF 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 Newer tests vs. gold standard Best tests for your population Validity in your population Accessibility Cost Capacity of local health care system Need a system in place to be able to screen AND to deal with positive results

60 Liquid-based Pap smear – the NEW test Patients without evidence of cervical cancer NO Cervical Cancer NO Cervical Cancer Standard Pap smear – the GOLD STANDARD

61 1. Are study methodology and results credible? 2. Have sensitivity, specificity and predictive values been calculated and reported? 3. Is the population tested similar to my patient population? 4. How can I use these results in a screening program or patient care? 5. Does this screening improve the present state of medical screening?

62 Lead time bias: over-estimation of survival rate among screening-detected cases When survival is calculated from diagnosis point Length bias: over-estimation of survival rate among screening-detected cases Due to excess of slowly progressing cases among those identified by screening Koretz: 2009

63 DiseaseTestTreatmentCostProgramming Condition 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 Definition: Identifying a disease that is unlikely to impact patient over lifetime Prostate or breast cancer may be present in body May never become clinically apparent Identifying pseudodisease is nearly impossible until person dies from unrelated causes Gold standard tests cannot predict future trajectory of a condition Durgin: 2005

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66 Mandated screening Genetic testing Disparities Creation of screening program

67 Newborn screening Syphilis testing for marriage licenses TB screening for health care workers Drug testing for airline pilots

68 Need to assess costs vs. benefits at all levels Individual Societal Healthcare system

69 Pros Identify serious problems that could harm others OR where immediate treatment is imperative Cons Potential harm to patient autonomy Confidentiality concerns Testing low risk population reduces PPV Consequences of false positive tests

70 Learn if individual carries a gene for a disease and might pass it on to children Screen unborn fetus for disease Test for genetic diseases in children or adults before symptoms emerge

71 Results difficult to interpret; not always clear cut Employment issues Health/life insurance consequences Added stress Costs Confidentiality Ownership of DNA Kalb, 2006

72 Geographic region Rural Inner city Uninsured and underinsured Screening and follow-up testing/treatment Cost-prohibitive without health insurance Minority and immigrant populations Lack of culturally competent healthcare providers Low health literacy

73 Cross-cultural differences in health literacy and attitudes Culturally relevant screening Screening practices may need to be adapted

74 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 Strategic targeting for screening Groups with higher prevalence – increase PPV Provider vs. patient – who is more likely to request? Growing body of evidence-based medicine allows us to: Identify more precise screening protocols Weigh benefits/drawbacks of screening test Strategic screening can be cost-effective

76 Screening is bedrock of secondary prevention Screening and diagnosis are not the same Sensitivity and specificity are characteristics of a screening test that determine a tests validity Predictive values are affected by sensitivity & specificity of test and by prevalence of the disease Screening of high-risk populations increases positive predictive value Screening decisions must weigh acceptability and applicability to practitioner, population, and individual

77 Department of Public Health Brody School of Medicine at East Carolina University Department of Community & Family Medicine Duke University School of Medicine

78 Mike Barry, CAE Lorrie Basnight, MD Nancy Bennett, MD, MS Ruth Gaare Bernheim, JD, MPH Amber Berrian, MPH James Cawley, MPH, PA-C Jack Dillenberg, DDS, MPH Kristine Gebbie, RN, DrPH Asim Jani, MD, MPH, FACP Denise Koo, MD, MPH Suzanne Lazorick, MD, MPH Rika Maeshiro, MD, MPH Dan Mareck, MD Steve McCurdy, MD, MPH Susan M. Meyer, PhD Sallie Rixey, MD, MEd Nawraz Shawir, MBBS

79 Sharon Hull, MD, MPH President Allison L. Lewis Executive Director O. Kent Nordvig, MEd Project Representative


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