Cadth 2015 a1 (gs090315)
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Transcript of Cadth 2015 a1 (gs090315)
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In Search of Efficiency, Consistency, Fairness, and
Impact in HTA:Modelling screening and treatment pathways
for diabetic retinopathy
Graham Scotland
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Acknowledgments
• Dr Helen Looker (University of Dundee)• Professor Helen Colhoun (University of Dundee)• Professor Paul McKeigue (University of Edinburgh)• Professor Graham Leese (NHS Tayside)• Dr John Olson (NHS Grampian)• Dr Sam Philip (NHS Grampain)
The work being presented was funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. The author accepts full responsibility for this presentation.
I am not aware of any actual or potential conflicts of interest in relation to this presentation
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Background
• Diabetic retinopathy / maculopathy – a leading cause of visual loss and blindness – proliferative retinopathy– macular oedema
• Early signs can be identified on retinal photographs• Early identification and treatment can reduce the risk
of visual loss• Scottish National Screening Programme established
in 2006
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The Scottish diabetic retinopathy screening programme
• Established in 2006, based on annual / 6-monthly screening using digital retinal photography
• Eligible screening population: 247,017• Number screened 199,268 (8% increase on previous
year)• Prevalence of diabetes growing by 4% annually • ~4% of patients referable in one annual round of
screening
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Diabetic retiopathy treatment pathways
• Severe background retinopathy (R3)– Monitor for progression to R4, and treat DMO if present
• Proliferative retinopathy (R4)– Pan-retinal photocoagulation – Vitrectomy (for complications of PDR)
• Maculopathy (M2) / diabetic macular oedema (DMO)– Monitor– Focal laser treatment (prevent moderate visual loss)– Intravitreal Anti-VEGF injections (for symptomatic disease)
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Cost-effectiveness of risk stratified screening intervals
• Risk of progression to referable disease associated with: – type of diabetes, duration of diabetes, sex, current
observed grade, prior observed grade (Looker et al., 2013)*
• Large proportion of the current annual screening cohort have progression risk < 1%
• Scope exists to improve efficiency of screening by adopting risk stratified screening intervals
*Looker HC et al. Predicted impact of extending the screening interval for diabetic retinopathy: the Scottish Diabetic Retinopathy Screening programme. Diabetologia. 2013; 56(8):1716-25
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Progression risks by sex, current/prior grade and duration of Type 2 diabetes
Current / prior gradeDuration of
diabetes (years)
Men - probability of any referable disease (%)
Women - probability of any referable disease
(%)
1 year 2 years 1 year 2 years
Current grade no DR /
0 0.14 0.39 0.14 0.375 0.20 0.64 0.23 0.69
10 0.26 0.90 0.31 1.0415 0.31 1.13 0.38 1.38
Current grade no DR / Prior grade no DR
0 0.07 0.25 0.08 0.255 0.11 0.43 0.13 0.48
10 0.14 0.61 0.18 0.7415 0.18 0.78 0.24 1.00
Current grade no DR / Prior grade mild DR
0 0.42 0.96 0.32 0.685 0.82 2.09 0.76 1.80
10 1.24 3.42 1.31 3.4015 1.61 4.63 1.84 5.04
*Looker HC et al. Predicted impact of extending the screening interval for diabetic retinopathy: the Scottish Diabetic Retinopathy Screening programme. Diabetologia. 2013; 56(8):1716-25
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Aim
Model the clinical and cost-effectiveness of adopting extended intervals for groups of patients defined by selected clinical and demographic variables routinely available to screening programmes.
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Conceptual screening model
Starting cohort Non-referable
screening participants (age,
sex, type of diabetes,
duration of diabetes,
current / previous grade)
In screening programme Referred
M2
R3/R4
R3/R4 +DMO
DMO
No DMO
R3
R4
Monitor
Monitor/ Treat
Monitor
Treat/ Monitor
Reduced risk of visual loss
Non-referable
Referable
M2
R3/R4
R3/R4 +DMO
Treat/ Monitor
Visual loss
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Some preliminary results
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Risk distribution in the annual screening cohort
Risk DecileRange of estimated one year risks of
progressionMin Max
1 0.000731 0.0009582 0.001005 0.0011543 0.001168 0.00134 0.00137 0.001445 0.001503 0.0017336 0.001746 0.0022547 0.002255 0.0081968 0.008634 0.0262259 0.026246 0.051352
10 0.051378 0.360943
Total 0.000731 0.360943
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Cost-effectiveness of biennial versus annual screening by risk decile
Progression risk 0.8-2.6%
Current practice: annual for all
Biennial for all
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Annual versus biennial screening by current / prior screened grade
Biennial for all with no DR / annual for everyone else
Biennial if no DR and no history of DR / annual for everyone else
Current practice: annual for everyone
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Summary of preliminary findings
• Annual screening appears unlikely to be cost-effective against accepted cost per QALY thresholds, if the 1-year forward risk of progression < ~1%
• Individuals with no retinopathy and no history of retinopathy (55% of the annual screening cohort) have an estimated risk <1%
• Adoption of biennial intervals in this group could lead to a substantial resource savings for very small QALY losses
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Further research plans
• Sub group analysis (by type of diabetes)
• Further characterisation of uncertainty
• Interaction between screening approach and variation in downstream treatment pathways
• Identify more efficient screening/treatment pathway configurations
• Improve and update the model over time
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Discussion
Benefits• Pathway modelling provides a flexible framework to inform changes in clinical pathways
over time• Individual level simulation can deal with complexity in the pathway and heterogeneity in the
cohort – Requires individual patient data
Challenges• Time consuming to build/debug/analyse• Limited availability of causal evidence can lead to many uncertainties
– Difficult to pin down precise estimates of cost-effectiveness– Extensive sensitivity analysis required– Difficult to validate
• Not a substitute for collecting primary randomised data to inform decision problems at different points in the care pathway