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Systematising the process : the role of PSMs in informing model structure. Jim Chilcott Technical Director, ScHARR-TAG Suzy Paisley DoH Research Scientist in Evidence Synthesis Paul Tappenden Senior OR Analyst Consensus Working Group on the Use of Evidence in Economic Decision Models

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systematising the process the role of psms in informing model structure

Systematising the process : the role of PSMs in informing model structure

Jim Chilcott

Technical Director, ScHARR-TAG

Suzy Paisley

DoH Research Scientist in Evidence Synthesis

Paul Tappenden

Senior OR Analyst

Consensus Working Group on the Use of Evidence in Economic Decision Models

MRC HSRC Workshop 26 September 2005

today s presentation
Today’s presentation
  • Define ‘structuring’ within the modelling process
  • Describe current practice
    • Evidence used
    • Tasks undertaken
  • Discuss ‘What role problem structuring methods (PSMs)?’

Consensus Working Group on the Use of Evidence in Economic Decision Models

defining model structuring
Defining model structuring
  • Disease and treatment pathway
  • Model scope
  • Modelling method

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice hta guidelines
Current practice:HTA Guidelines

HTA guidelines (n=32)

None 17 (53%)

Description 2 (6%)

Justification 4 (13%)

Sensitivity analysis 5 (16%)

Not available 4 (13%)

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice modelling guidelines philips et al 2004
Statement of problem

Justification of approach

Scope / perspective

Structural assumptions

Consistency

Strategies / comparators

Model type

Time horizon

Health states

Cycle length

Parsimony

Current practice:Modelling guidelines (Philips et al.,2004)

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice reported cooper et al 2005
Current practice:Reported (Cooper et al., 2005)

HTA monographs (n=42)

Diagram of model 26 (62%)

Model structure

and assumptions discussed 5 (12%)

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice observed
Current practice:Observed
  • 8 case study projects
  • Description model structuring process
  • Short, semi-structured interviews
  • Examination of corresponding study reports

Consensus Working Group on the Use of Evidence in Economic Decision Models

evidence consulted
Evidence consulted

Consensus Working Group on the Use of Evidence in Economic Decision Models

reporting
Reporting

Consensus Working Group on the Use of Evidence in Economic Decision Models

summary of themes
Summary of themes
  • Model structure amended according to data availability
  • Clinician input (1st order validation)
  • Existing models consulted as 1st step
  • Iterative structuring process
  • Complexity of structure shifted both ways
  • Very limited reporting process of development
  • MSc dissertation provided most transparent reporting

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice evidence used
Clinical expertise

Published evidence

Existing models

Natural history

Treatment pathway

Modelling method

Effectiveness evidence

Current practice:Evidence used

Consensus Working Group on the Use of Evidence in Economic Decision Models

current practice tasks undertaken
Current practice:Tasks undertaken
  • Iteration
  • Consultation
  • Evaluation and comparison
  • Feedback and clarification
  • Decisions regarding simplicity, complexity, feasibility and inconsistency

Consensus Working Group on the Use of Evidence in Economic Decision Models

why psms
Why PSMs?
  • Lack of transparency
  • Data modelling vs problem modelling
  • Validity of model (unquestioned question)
  • Issues that ‘can’t be modelled’
  • ‘Not qualified to comment’

Consensus Working Group on the Use of Evidence in Economic Decision Models

why psms1
Why PSMs?
  • Data led models vs evidence informed models
  • Use of expert opinion
  • Implicit use of PSM methods
  • Observed usefulness of action research process

Consensus Working Group on the Use of Evidence in Economic Decision Models

psms msms

?

PSMs / MSMs

Messes Problems

SODA

SSM

SCA

Robustness Analysis

Drama Theory

Decision Conferencing

Decision analysis

Markov

Queuing theory

Simulation

Game Theory

Consensus Working Group on the Use of Evidence in Economic Decision Models

characteristics of psms
Characteristics of PSMs
  • Techniques to facilitate exploration / definition of a problem situation
  • Group based
  • Uncovering options
  • Enabling group action
  • Accepting uncertainty
  • Managing conflict
  • Facilitator - analyst

Consensus Working Group on the Use of Evidence in Economic Decision Models

slide18
SODA

Individual interviews =>

Merge maps =>

Group workshops =>

Commitment to action

Cognitive maps

Group map

Expand/refine map

Group ownership

Consensus Working Group on the Use of Evidence in Economic Decision Models

slide19
SSM

Consensus Working Group on the Use of Evidence in Economic Decision Models

slide20
Pros
  • Problem structuring, not problem solving
  • Gathering information, generating ideas
  • Retain flexibility in early stages
  • Demonstrate understanding of complexity, diversity and inconsistency
  • Prioritising and simplifying

Consensus Working Group on the Use of Evidence in Economic Decision Models

slide21
Cons
  • Methods development required
  • Adaptation to HTA context
  • New skills
  • Ownership
  • Facilitation of group decision making
  • Reproducibility

Consensus Working Group on the Use of Evidence in Economic Decision Models

developing a mixed method
Developing a mixed method

Qualitative model structuring process to inform quantitative decision-making process.

‘Soft’ qualitative structuring process

‘Hard’ analytic

methods

Consensus Working Group on the Use of Evidence in Economic Decision Models

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