Utilizing Biostatistics in Diagnosis, Screening, and Prevention Presentation 3 of 6

Learning Objectives Review important statistical concepts and understand how to apply them to support high value care decisions when considering diagnostic and screening tests and proposed treatments Define the four categories of preventive care Explore the benefits and harms (including cost) of routine screening Use electronic tools to identify preventive measures that will provide high value for your patients Examine the evidence supporting your recommendations Develop an approach to customize preventive care recommendations to an individual patient and his/her unique risk factors, values, and concerns

Essential Biostatistical Concepts Pretest and Posttest probability Sensitivity and Specificity Positive/Negative Predictive Values Likelihood Ratios Number Needed to Treat/Harm Disease Positive Disease Negative Test Positive ab Test Negative cd

Likelihood Ratios Using likelihood ratios: 1.Use the estimated pretest probability of disease as an anchor on the left side of the graph 2.Draw a straight line through the known likelihood ratio, either (+) or (-) 3.Where this line intersects the graph on the right represents the posttest probability of disease

Role of Diagnostic Tests To reduce uncertainty regarding a specific patient’s diagnosis Generally most appropriate for patients you feel have an intermediate (10-90%) pre-test probability of a disease (Ex. Centor criteria for Strep pharyngitis) Test characteristics (i.e. likelihood ratios) should be considered before ordering a test to help determine whether a given test would significantly alter your pre-test probability (and thus affect management) (Ex. if you estimate a patient’s pretest probability to be 10% but the LR of a diagnostic test is only 2, then a positive test result will still only yield around a 25% posttest probability )

Approach To Chest Pain: Small Group Exercise Break into 3 small groups Each group will work through a different case of chest pain Focus on the diagnostic process: Estimating the pretest probability of disease in your patient Evaluate how cardiac stress testing in your patient would influence your pretest probability of disease Assess whether you believe that cardiac stress testing would be helpful in your patient Be prepared to briefly summarize your findings and share them with the larger group

Preventive Practice: The Periodic Health Examination A 57-year-old woman presents for her periodic health examination. She has not been seen by a doctor for ten years She has no past medical history except for a hysterectomy for fibroids 10 years ago. She takes no medications She is a retired teacher, lives alone, smokes 1 pack per day (38 pack years), does not use alcohol or illicit drugs, and has not been sexually active since her husband died 8 yrs ago She has no family history of cancer, vascular disease, or osteoporosis Her BP 135/83 and her BMI is 24, the remainder of her exam is unremarkable

What Should be Included in her Preventive Care? Rank the top five preventive services you might offer this patient. Use the categories below to help you. Immunizations Screening Behavioral counseling to motivate lifestyle changes Chemoprevention

Preventive Care Menu Influenza vaccine Pneumococcal vaccine Td/TDAP Zoster vaccine Smoking cessation Weight loss Exercise Alcohol misuse Aspirin Statin therapy Hepatitis C screening Calcium/Vitamin D Tamoxifen Mammogram Colonoscopy Pap smear HIV screening Lung cancer screening (LDCT) DEXA scan HbA1C Fasting lipid panel Domestic violence screening

Role of Screening Tests To detect asymptomatic and early stage disease Should be highly sensitive and highly specific to pick up most cases of true disease and avoid false positives Targeted toward populations with a higher disease prevalence (high positive predictive value) Should be relatively safe and cost-effective Should screen for diseases in which early identification and treatment have been demonstrated to improve clinical outcomes

Cost-effectiveness 1 Measures that cost money but improve health can be further categorized by their cost, often measured in dollars per QALY (quality-adjusted life-year) QALYs incorporate an estimate of the quantity of life gained by the intervention, coupled with a more subjective assessment of the quality of that life affected by the intervention Historically, payers have considered any intervention that has a cost-effectiveness ratio of <$100K per QALY as acceptable “Cost-saving” Reduces cost, Costs money, Costs money, Improves health Improves health Worsens health

Cohen J, Neumann P, Weinstein M NEJM 2008:358;7 2

Common Harms Associated with Screening False positive results Can lead to incorrect labeling, inconvenience, expense, and physical harm in follow-up tests “Overdiagnosis 3 ” and “Pseudodisease” (Length-time bias)

USPSTF Recommendation Grades, Electronic Preventive Services Selector (ePSS), and Vaccine Scheduler USPSTF provides a tool for clinicians (ePSS) to search for graded recommendations. epss.ahrq.gov/PDA/index.jsp Vaccine recommendations are available in the second tool. The ACP also offers a downloadable Immunization Advisor, listed below. immunization.acponline.org/app/

USPSTF Recommendation Grades GradeDefinition AThe USPSTF recommends the service. There is high certainty that the net benefit is substantial. 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 Note: The following statement is undergoing revision. Clinicians may provide this service to selected patients depending on individual circumstances. However, for most individuals without signs or symptoms there is likely to be only a small benefit from this service. D The 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. I StatementThe USPSTF concludes that current evidence is insufficient to assess the balance of benefits & harms of the service.

Lets Plug our Patient into the ePSS Calculator epss.ahrq.gov/PDA/index.jsp Compare your top 5 to their top five: 1.Aspirin for chemoprevention of CVD – grade A 2.Colorectal cancer screening – grade A 3.Lipid screening- grade A 4.Tobacco use counseling and intervention – grade A 5.Combined influenza/pneumococcal vaccine (not in calculator)

Balancing Benefits and Harms 4 Daily ASA use results in a 17% absolute risk reduction in ischemic CVA for women and 32% absolute risk reduction for MI in men Major risk of daily ASA use is serious upper GI bleed Both the risk of major GI bleed (net harm) and the risk of ischemic CVA (net benefit) increase with age Using data from large randomized controlled trials, USPSTF has provided tables that estimate the absolute # of strokes and MI prevented per 1000 women and men, respectively, stratified by baseline stroke risk and age Baseline 10-yr CVA risk can be calculated using: = 3.5% for our patient

Balancing benefits and harms 4

What about for this patient? Mr. T is a 50 yo male who comes to your office for routine follow-up He has heard that taking an aspirin may decrease his risk of a heart attack and is wondering whether he should start taking daily aspirin Past medical history No family history of CAD No personal history of CAD or gastrointestinal issues His only medical history of HTN, well controlled with medication His recent lipid profile shows total cholesterol of 160, HDL 50 PE in office with normal cardiac and general exam, BP 110/74 How would you counsel him? What is the data? Use Framingham risk assessment calculator (10 yr MI risk) at hp2010.nhlbihin.net/atpiii/calculator.asp = 2%

Summary Diagnostic tests should only be used if the result is likely to significantly affect your certainty of a disease (posttest probability) and should rely on likelihood ratios for a given test when available Preventive healthcare must be individualized with the help of expert recommendations (USPSTF) to offer patients interventions that are most likely to positively impact their long-term healthcare goals Recommendations are not prescriptive, but rather the beginning of an open dialogue with patients to create (as a team) a prioritized plan of preventive health maintenance

Commitment in your Practice Think about your approach to diagnostic and screening tests Do you routinely make recommendations that are not in line with the high value principles outlined in this module? Write down at least one thing to Start doing and one thing to Stop doing START: STOP:

References 1.Owens D, et al. High-value, cost-conscious health care: concepts for clinicians to evaluate the benefits harms and costs of medical interventions. Ann Intern Med. 2011; 154: Cohen JT, et al. Does preventive care save money? Health economics and the presidential candidates. N Engl J Med. 2008; 358: Moynihan R, et al. Preventing overdiagnosis: how to stop harming the healthy. BMJ. 2012; 344: e U.S. Preventive Services Task Force; Aspirin for the Prevention of Cardiovascular Disease: U.S. Preventive Services Task Force Recommendation Statement. Annals of Internal Medicine Mar;150(6):