bayesian hierarchical models for the design and analysis ... · • bayes rule is a logic for...
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Bayesian Hierarchical Models for the Design and Analysis of Studies to Individualize HealthcareScott L. ZegerJohn C. Malone Professor of Biostatistics and Medicine@ScottZegerSeptember 19, 2019
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Scott Zeger
DisclosuresRelationship Company(ies)
Speakers Bureau
Advisory Committee Embold Health
Board Membership
Consultancy
Review Panel
PCORI Funding PCORI ME-1408-20318
Honorarium
Ownership Interests
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Outline• A learning healthcare system aspires to:
Improve each clinical decision for this patient by learning from the experiences of prior similar patients: population individual
• Bayes rule is a logic for learning
• Prostate cancer application
• Lessons learned from implementation of learning systems within a major academic health center
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Healthcare Decisions: Be A CLINICIAN for this moment• Presentation: 40-year-old man, no family history, tests positive for a life-threatening
disease in a routine screen• Clinical Questions: What is his disease state? What action do you recommend?• Decision Support: Data from prior population of similar people
True disease status
Exam result Yes No Total
Positive 15 985 1,000
Negative 5 8,995 9000
Total 20 9,980 10,000
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Bayes Rule
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Why Bayes?• Focus on each patient• Use probability as a natural measure of uncertainty• Integrate population-based evidence with expert judgement• Reflects how clinicians reason• Earlier rule-based expert systems largely failed
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Learning from prior patients’ experience
• Using Bayes rule, create the computational analogue of the 2x2 table for any complex measurements
Population Individual
• Build capacity to make tables for ever-narrower sets of “otherwise-similar” individuals
Subset, Subset, Subset
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Prostate Cancer Application (Bal Carter, Yates Coley, Ken Pienta, Mufaddal Mamawala, Scott Zeger, TIC, APL, IT@JH, JHTV)
Clinical questions about active surveillance:1. Given the data collected to date on this
individual, should we do another biopsy today?2. If we remove his prostate today, what is the
probability the tumor is aggressive vs indolent?
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Learning Health System Steps Prostate Cancer Active Surveillance Example Challenges
Frame unmet health/clinical need Half of active surveillance prostatectomies yield indolent cancers
Specify biomedical model Predictors of indolence: PSA, biopsies, family history, genomic score, MRI
Poor understanding of mechanisms
Wrangle relevant data into a clinical cohort database (CCDB) from which to learn through careful analysis
Brady Institute Active Surveillance clinical cohort database with 1300 men; Precision Medicine Analytics Platform (PMAP)
Learning-grade data not collected;Data collected but “locked-up in EHR; HIPAA “minimum necessary standard”
Design and test decision tool Coley, et al (a, b): Bayesian hierarchical model Inadequate predictive power;External validity checks not made
Design and test users’ interface for population health manager, clinician, and/or patient
PCORI ME-1408-20318 / TIC EHR has limited capacity for visualization, calculation, but ”owns the workflow”; $300K for two pages in EPIC
Design and test on-going curation JHM Committee No standards; must create policies and procedures
Devise business model to sustain/improve tool
?? New methods improve outcomes at lower costs; providers lose money
Scale up and out for broad use CoE in a Box; Partners Takes capital investments and time
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Learning Healthcare System
Learning Healthcare System of Systems – JHM Precision Medicine Centers of Excellence (PMCOEs)
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PMAP – Precision Medicine Analytics Platform
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Learn More
• Scott L. Zeger, PhD