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Module 4: Screening Developed through the APTR Initiative to Enhance Prevention and Population Health Education in collaboration with the Brody School.

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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: Screening 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 Acknowledgments 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 Cheryl Reeves, MS, MLS 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 Presentation Objectives
Define screening and identify appropriate conditions for screening Evaluate screening tests in terms of their validity, results and generalizability Evaluate the effectiveness of a screening program and discuss the common biases Discuss ethical considerations in screening

4 Introduction to Screening

5 Oprah’s Full Body Scan 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 Preventive Medicine & Public Health
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 Prevention – Brief Overview
Primary Prevention Secondary Prevention Tertiary Prevention McKenzie et al.: 2008

8 Screening Defined 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 Importance of Screening
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-Diagnosis Connection
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 Screening versus Diagnostic Tests
Screening Test Diagnostic Test

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

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

14 Characteristics of a Good Screening Test
Simple Rapid Inexpensive Safe Available Acceptable

15 Common Screening Tests

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 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 Common Wellness Screenings
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 Breast Cancer Screening
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 Colon Cancer Screening
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 Case Study Colorectal Cancer Screening
Practice evaluation of diagnostic test characteristics and screening programs Discuss prevention concepts Apply this at patient and population level

22 Newborn Screening 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 Newborn health screening—mandatory screen for disorders, such as metabolic, hormonal, blood, and infectious conditions. States vary in what diseases test for For example, NY tests for over 40 conditions, including HIV. Heel prick blood test done hours post birth Most 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.

23 Evaluation of Screening Tests

24 Evaluating Tests 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 Characteristics of a Screening Test
VALIDITY and RELIABILITY Fortune & Reid: 1998

26 Reliability 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 Common Types of Reliability
Intra-subject Jekel: 1996; Al-Eisa: 2009

28 Common Types of Reliability
Intra-rater Intra-subject Jekel: 1996; Al-Eisa: 2009

29 Common Types of Reliability
Intra-rater Intra-subject Inter-rater Jekel: 1996; Al-Eisa: 2009

30 Common Types of Reliability
Intra-rater Intra-subject Inter-rater Instrument Jekel: 1996; Al-Eisa: 2009

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

33 Relationship Between Sensitivity and Specificity
PSA level Sensitivity Specificity 1.0 100 21 2.0 48 3.0 60 4.0 99 73 5.0 96 76 6.0 94 79 7.0 90 83 8.0 88 9.0 68 10.0 54 93 11.0 47 12.0 30 95 13.0 23 14.0 17 97 15.0 11 Morgan TO et al; NEJM, 1996

34 The 2x2 Table True Positive False Positive False Negative
Disease Present Disease Absent True Positive False Positive Test + False Negative True Negative Test -

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

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

37 Predictive Values Positive predictive value Negative predictive value

38 Positive Predictive Value (PPV)
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 Negative Predictive Value (NPV)
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 Test Characteristics and Population Tested
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 Predictive Value and Prevalence (in test with 98% sensitivity, 92% specificity)

42 Predictive Values Sample Calculations
Disease Diseased Non-Diseased PVs Test Result Positive True 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 + FN Specificity TN + FP

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

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

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

46 Multiple Screening Tests Simultaneous
Use of different tests concurrently to screen for same condition Example: Prenatal multiple marker screening for Down Syndrome Measures levels of 3 biomarkers in mother’s 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 Multiple Screening Tests Sequential
Use of two-stage screening to target testing efforts Example: Early pregnancy gestational diabetes screening First trimester risk assessment—identifies women at higher risk of gestational diabetes Oral 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 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

49 Effectiveness of Screening Programs

50 Screening Effectiveness Evaluation
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 Study Design Testing a Test
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

52

53 USPSTF Activities 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 USPSTF Methodology Define analytic framework – outcomes & questions
Define and retrieve relevant evidence Evaluate 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 Benefit Link 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 Benefit Magnitude of Net Benefit Substantial Moderate Small Zero/negative High A B C D Low Insufficient (I Statement) Courtesy of Diana Pettiti, USPSTF: 2010 57

58 Communicating USPSTF Recommendations
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. 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 Comparison of Screening Tools
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 Testing a Test Cervical Cancer NO Cervical Cancer Patients without
Liquid-based Pap smear – the NEW test NO Cervical Cancer Patients without evidence of cervical cancer Cervical Cancer Standard Pap smear – the GOLD STANDARD NO Cervical 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 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 To Screen or Not to Screen Essential Criteria
Disease Test Treatment Cost Programming 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 Pseudodisease 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

65 Screening and Ethics

66 Ethical Considerations
Mandated screening Genetic testing Disparities Creation of screening program

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

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

69 Mandatory Screening Pros Cons
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 Genetics Testing Benefits
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 Genetic Testing Concerns
Results difficult to interpret; not always clear cut Employment issues Health/life insurance consequences Added stress Costs Confidentiality Ownership of DNA Kalb, 2006

72 Disparities Access to Screening
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 Disparities Cultural Cross-cultural differences in health literacy and attitudes Culturally relevant screening Screening 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 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 Summary 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 test’s 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 Collaborating Institutions
Department of Public Health Brody School of Medicine at East Carolina University Department of Community & Family Medicine Duke University School of Medicine

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

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


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