1. Models to Inform Recommendations About Preventive Services Perspective of the United States Preventive Services Task Force

2. Behavioral interventions Behavioral interventions –inability to maintain fidelity with treatment –inability to control provider effects Quality improvement interventions Quality improvement interventions –inconsistency of implementation –difficulty in withholding interventions with what is viewed as high face validity –contamination An RCT for Every Topic is an Unattainable Goal: Technical

3. Community programs Community programs –Insufficient number of communities willing to be randomized –Inability to maintain fidelity with program parameters –Need for adaptability to gain cooperation –Need for adaptability to achieve effectiveness –Contamination An RCT for Every Topic is an Unattainable Goal: Technical

4. The Parachute Problem Do we really NEED an RCT? Do we really NEED an RCT? “....the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials....we think that everyone might benefit if the most radical protagonists of evidence-based medicine organized and participated in a double-blind, randomized, placebo-controlled crossover trial of the parachute....” Sackett. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. BMJ 2003;327:1459-61.

5. It is not feasible to conduct an RCT for every topic for which clinical decisions must be made It is not feasible to conduct an RCT for every topic for which clinical decisions must be made But Even More Importantly

6. CRC: Options in 2008 Something found in stool Something found in stool –Occult blood using guaiac (gFOBT) Un-rehydrated Un-rehydrated Rehydrated Rehydrated –Occult blood using test that is more sensitive than guaiac –Fecal DNA Something “seen” in the colon Something “seen” in the colon –Visual Flexible sigmoidoscopy Flexible sigmoidoscopy –Alone –With FOBT (several options) Colonoscopy Colonoscopy –Radiographic Dual contrast barium enema (DCBE) Dual contrast barium enema (DCBE) CT colonography (CTC) CT colonography (CTC)

7. Number of RCTs: CRC Screening Type of Test 9 strategies against no screening 9 strategies against no screening Would require 8 two-arm trials or a very large 8-arm trial (unrehydrated gFOBT already done) Would require 8 two-arm trials or a very large 8-arm trial (unrehydrated gFOBT already done) 9 strategies against all other possible strategies alone 9 strategies against all other possible strategies alone E.g. more sensitive FOBT versus unrehydrated FOBT FOBT versus optical colonoscopy FOBT versus optical colonoscopy optical colonoscopy versus CT colonography optical colonoscopy versus CT colonography flexible sigmoidoscopy versus fecal DNA etc. etc. etc. flexible sigmoidoscopy versus fecal DNA etc. etc. etc. Would require 35 two-arm trials or a very large 8-arm trial

8. Starting age Starting age –Age 40 or 50 or something else for CRC –Age 16 or 21 or something else for cervical cancer Stopping age Stopping age –Stop age 75 versus 85 for CRC –Stop age 65 versus 75 for cervical cancer Screening interval Screening interval –Every 5 years versus every 10 years versus once in a lifetime for CRC –Every year versus every 3 years versus every 5 years for cervical cancer It May be Impossible or Nearly Impossible To Conduct a Valid RCT

9. Long-Term Financial Planning Long-Term Financial Planning –What if I live to age 95, how much money will I need to live comfortably considering inflation and the rate of return on my investments? (MAKE A MODEL) –What do you recommend to assure that I don’t run out of money? (USE THE MODEL TO INFORM THE RECOMMENDATION) Models: What If.....

10. Short-Term Financial Decisions Short-Term Financial Decisions –What if I buy a car that gets 65 miles per gallon, how much money will I save over five years considering the number of miles I drive? (MAKE A MODEL). –Should I buy a car that costs $34,000? (USE THE MODEL TO INFORM THE DECISION) Models: What If.....

11. Policies Policies –What if people in developing economies use the same number of barrels of crude oil per capita as people in the United States, in what year will the world supply of crude oil be exhausted? (MAKE A MODEL) –What does the committee recommend to assure that there is sufficient availability of energy for future generations? (USE THE MODEL TO INFORM THE RECOMMENDATION) Models: What If.....

12. Daily Decisions Daily Decisions –What if I leave the office at 3 o’clock instead of 5 o’clock, how long will it take to get back home over the Bay Bridge considering the month, the day of the week and the weather? (MAKE A MODEL). –Should I leave early today to be sure that I am not late to dinner at the Smiths? (USE THE MODEL TO INFORM THE DECISION) Models: What If.....

13. Conscientious: careful, thorough, meticulous Conscientious: careful, thorough, meticulous Explicit: open, clear, plain Explicit: open, clear, plain Judicious: sensible, well thought out Judicious: sensible, well thought out Models in the Context of Evidence-Based Medicine Modelers need to do this better Good models meet this criterion

14. Start Age Stop Age Interval Estimated Number of Life-years Gained per 1,000 Screened Test for cancer A 2065 5 yrs 265 Test for cancer A 2565 5 yrs 263 Test for cancer A 3065 5 yrs 243 Results From Good Models: Does This Information Help Make a Recommendation? The USPSTF Thinks the Answer is Yes.

15. Start Age Stop Age Interval Estimated Number of Life-years Gained per 1,000 Screened Test for cancer B 4085 8 yrs 301 Test for cancer B 4085 15 yrs 267 Test for cancer B 4085once244 Results From Good Models: Does This Information Help Make a Recommendation? The USPSTF Thinks the Answer is Yes.

16. Not taught in most medical schools Not taught in most medical schools Generalized antipathy; many people hate anything called a model Generalized antipathy; many people hate anything called a model Assumptions are made; these often look like guesses Assumptions are made; these often look like guesses The model assumptions are often opaque The model assumptions are often opaque Models: the Pushback

17. MODELS Information from models reduces bounds estimates Information from models reduces bounds estimates Information from models is better than information obtained by guessing, even informed guessing Information from models is better than information obtained by guessing, even informed guessing A recommendation based on a good model is better than silence and is often the best we will ever do A recommendation based on a good model is better than silence and is often the best we will ever do

18. All models are wrong, some are useful. George Box 1979 George Box 1979

19. DISCUSSION