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

Models to Inform Models to Inform Recommendations About Recommendations About Preventive ServicesPreventive Services

Perspective of the United States Perspective of the United States Preventive Services Task ForcePreventive Services Task Force

Behavioral interventionsBehavioral interventions– inability to maintain fidelity with treatmentinability to maintain fidelity with treatment– inability to control provider effectsinability to control provider effects

Quality improvement interventionsQuality improvement interventions– inconsistency of implementationinconsistency of implementation– difficulty in withholding interventions with what is viewed as difficulty in withholding interventions with what is viewed as

high face validityhigh face validity– contaminationcontamination

An RCT for Every Topic is an An RCT for Every Topic is an Unattainable Goal: Unattainable Goal: TechnicalTechnical

Community programs Community programs – Insufficient number of communities willing to be Insufficient number of communities willing to be

randomizedrandomized– Inability to maintain fidelity with program parametersInability to maintain fidelity with program parameters– Need for adaptability to gain cooperationNeed for adaptability to gain cooperation– Need for adaptability to achieve effectivenessNeed for adaptability to achieve effectiveness– ContaminationContamination

An RCT for Every Topic is An RCT for Every Topic is an Unattainable Goal: an Unattainable Goal: TechnicalTechnical

The Parachute The Parachute ProblemProblem Do we really NEED an RCT?Do we really NEED an RCT?

““....the effectiveness of parachutes has not been ....the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised subjected to rigorous evaluation by using randomised controlled trials....we think that everyone might controlled trials....we think that everyone might benefit if the most radical protagonists of evidence-benefit if the most radical protagonists of evidence-based medicine organized and participated in a based medicine organized and participated in a double-blind, randomized, placebo-controlled double-blind, randomized, placebo-controlled crossover trial of the parachute....”crossover trial of the parachute....”

Sackett. Parachute use to prevent death and major Sackett. Parachute use to prevent death and major trauma related to gravitational challenge: systematic trauma related to gravitational challenge: systematic review of randomised controlled trials. BMJ review of randomised controlled trials. BMJ 2003;327:1459-61.2003;327:1459-61.

It is not It is not feasiblefeasible to conduct an to conduct an RCT for every topic for which RCT for every topic for which clinical decisions must be madeclinical decisions must be made

But Even More But Even More ImportantlyImportantly

CRC: Options in 2008CRC: Options in 2008

Something found in stoolSomething found in stool– Occult blood using guaiac (gFOBT)Occult blood using guaiac (gFOBT)

Un-rehydratedUn-rehydrated RehydratedRehydrated

– Occult blood using test that is more sensitive than Occult blood using test that is more sensitive than guaiacguaiac

– Fecal DNAFecal DNA Something “seen” in the colonSomething “seen” in the colon

– VisualVisual Flexible sigmoidoscopyFlexible sigmoidoscopy

– AloneAlone– With FOBT (several options)With FOBT (several options)

ColonoscopyColonoscopy– RadiographicRadiographic

Dual contrast barium enema (DCBE)Dual contrast barium enema (DCBE) CT colonography (CTC)CT colonography (CTC)

Number of RCTs: CRC Number of RCTs: CRC Screening Type of TestScreening Type of Test 9 strategies against no screening9 strategies against no screening Would require 8 two-arm trials or a very large 8-arm Would require 8 two-arm trials or a very large 8-arm

trial (unrehydrated gFOBT already done)trial (unrehydrated gFOBT already done)

9 strategies against all other possible 9 strategies against all other possible strategies alonestrategies aloneE.g. more sensitive FOBT versus unrehydrated FOBTE.g. more sensitive FOBT versus unrehydrated FOBT FOBT versus optical colonoscopyFOBT versus optical colonoscopy optical colonoscopy versus CT colonographyoptical 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-Would require 35 two-arm trials or a very large 8-

arm trialarm trial

Starting ageStarting age– Age 40 or 50 or something else for CRCAge 40 or 50 or something else for CRC– Age 16 or 21 or something else for cervical cancerAge 16 or 21 or something else for cervical cancer

Stopping ageStopping age– Stop age 75 versus 85 for CRCStop age 75 versus 85 for CRC– Stop age 65 versus 75 for cervical cancerStop age 65 versus 75 for cervical cancer

Screening intervalScreening interval– Every 5 years versus every 10 years versus once in Every 5 years versus every 10 years versus once in

a lifetime for CRCa lifetime for CRC– Every year versus every 3 years versus every 5 Every year versus every 3 years versus every 5

years for cervical canceryears for cervical cancer

It May be Impossible or Nearly It May be Impossible or Nearly Impossible To Conduct a Valid Impossible To Conduct a Valid RCTRCT

Long-Term Financial Planning Long-Term Financial Planning – What if I live to age 95, how much money What if I live to age 95, how much money

will I need to live comfortably considering will I need to live comfortably considering inflation and the rate of return on my inflation and the rate of return on my investments? (MAKE A MODEL) investments? (MAKE A MODEL)

– What do you recommend to assure that I What do you recommend to assure that I don’t run out of money? (USE THE don’t run out of money? (USE THE MODEL TO INFORM THE MODEL TO INFORM THE RECOMMENDATION)RECOMMENDATION)

Models: What If.....Models: What If.....

Short-Term Financial Decisions Short-Term Financial Decisions – What if I buy a car that gets 65 miles What if I buy a car that gets 65 miles

per gallon, how much money will I save per gallon, how much money will I save over five years considering the number over five years considering the number of miles I drive? (MAKE A MODEL). of miles I drive? (MAKE A MODEL).

– Should I buy a car that costs $34,000? Should I buy a car that costs $34,000? (USE THE MODEL TO INFORM THE (USE THE MODEL TO INFORM THE DECISION)DECISION)


Policies Policies – What if people in developing economies use What if people in developing economies use

the same number of barrels of crude oil per the same number of barrels of crude oil per capita as people in the United States, in capita as people in the United States, in what year will the world supply of crude oil what year will the world supply of crude oil be exhausted? (MAKE A MODEL) be exhausted? (MAKE A MODEL)

– What does the committee recommend to What does the committee recommend to assure that there is sufficient availability of assure that there is sufficient availability of energy for future generations? (USE THE energy for future generations? (USE THE MODEL TO INFORM THE RECOMMENDATION)MODEL TO INFORM THE RECOMMENDATION)


Daily Decisions Daily Decisions – What if I leave the office at 3 o’clock What if I leave the office at 3 o’clock

instead of 5 o’clock, how long will it take instead of 5 o’clock, how long will it take to get back home over the Bay Bridge to get back home over the Bay Bridge considering the month, the day of the considering the month, the day of the week and the weather? (MAKE A MODEL). week and the weather? (MAKE A MODEL).

– Should I leave early today to be sure that Should I leave early today to be sure that I am not late to dinner at the Smiths? I am not late to dinner at the Smiths? (USE THE MODEL TO INFORM THE (USE THE MODEL TO INFORM THE DECISION)DECISION)


Conscientious: careful, thorough, Conscientious: careful, thorough, meticulousmeticulous

Explicit: open, clear, plainExplicit: open, clear, plain

Judicious: sensible, well thought Judicious: sensible, well thought outout

Models in the Context Models in the Context of Evidence-Based of Evidence-Based MedicineMedicine

Modelers need to do this better

Good models meet this criterion

Good models meet this criterion

Start Start AgeAge

Stop Stop AgeAge IntervalInterval

Estimated Number Estimated Number of Life-years of Life-years Gained per 1,000 Gained per 1,000 ScreenedScreened

Test for cancer Test for cancer AA 2020 6565 5 yrs5 yrs 265265



Results From Good Models: Does This Results From Good Models: Does This Information Help Make a Information Help Make a Recommendation? Recommendation? The USPSTF Thinks the Answer is Yes.The USPSTF Thinks the Answer is Yes.

Start Start AgeAge

Stop Stop AgeAge IntervalInterval

Estimated Number Estimated Number of Life-years of Life-years Gained per 1,000 Gained per 1,000 ScreenedScreened

Test for cancer Test for cancer BB 4040 8585 8 yrs8 yrs 301301

Test for cancer Test for cancer BB 4040 8585 15 yrs15 yrs 267267

Test for cancer Test for cancer BB 4040 8585 onceonce 244244

Results From Good Models: Does This Results From Good Models: Does This Information Help Make a Information Help Make a Recommendation? Recommendation? The USPSTF Thinks the Answer is Yes.The USPSTF Thinks the Answer is Yes.

Not taught in most medical schools Not taught in most medical schools Generalized antipathy; many people Generalized antipathy; many people

hate anything called a modelhate anything called a model Assumptions are made; these often Assumptions are made; these often

look like guesses look like guesses The model assumptions are often The model assumptions are often

opaqueopaque

Models: the Pushback Models: the Pushback

MODELSMODELS

Information from models reduces Information from models reduces bounds estimatesbounds estimates

Information from models is better Information from models is better than information obtained by than information obtained by guessing, even informed guessingguessing, even informed guessing

A recommendation based on a A recommendation based on a good model is better than silence good model is better than silence and is often the best we will ever and is often the best we will ever dodo

All models are wrong, some are All models are wrong, some are useful.useful.

George Box 1979George Box 1979

DISCUSSIONDISCUSSION

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