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Cover of Development of a cost-effectiveness model for optimisation of the screening interval in diabetic retinopathy screening

Development of a cost-effectiveness model for optimisation of the screening interval in diabetic retinopathy screening

Health Technology Assessment, No. 19.74

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Author Information
Southampton (UK): NIHR Journals Library; .

Headline

The study developed two stratification models for an individual's risk of future development of sight-threatening diabetic retinopathy (STDR): the first using only results from previous screening events and the second using previous screening and some commonly available GP data. The estimates from both models were capable of clearly differentiating groups at low-, medium- and high-risk of future development of STDR. The rate of progression to STDR was 5 per 1000 person-years (PYs) in the lowest decile of risk and 75 per 1000 PYs in the highest decile. The models were further validated in three independent datasets. The study found that annual screening for STDR was not cost-effective. The most cost-effective option was to screen every 3 years. However, risk stratification and personalised screening intervals could improve the cost-effectiveness of the screening programme. Screening patients in low-risk groups every 5 years and those in high-risk groups every 2 years were the most cost-effective strategies. There was however considerable uncertainty in the estimated incremental costs and quality-adjusted life-years.

Abstract

Background:

The English NHS Diabetic Eye Screening Programme was established in 2003. Eligible people are invited annually for digital retinal photography screening. Those found to have potentially sight-threatening diabetic retinopathy (STDR) are referred to surveillance clinics or to Hospital Eye Services.

Objectives:

To determine whether personalised screening intervals are cost-effective.

Design:

Risk factors were identified in Gloucestershire, UK using survival modelling. A probabilistic decision hidden (unobserved) Markov model with a misgrading matrix was developed. This informed estimation of lifetime costs and quality-adjusted life-years (QALYs) in patients without STDR. Two personalised risk stratification models were employed: two screening episodes (SEs) (low, medium or high risk) or one SE with clinical information (low, medium–low, medium–high or high risk). The risk factor models were validated in other populations.

Setting:

Gloucestershire, Nottinghamshire, South London and East Anglia (all UK).

Participants:

People with diabetes in Gloucestershire with risk stratification model validation using data from Nottinghamshire, South London and East Anglia.

Main outcome measures:

Personalised risk-based algorithm for screening interval; cost-effectiveness of different screening intervals.

Results:

Data were obtained in Gloucestershire from 12,790 people with diabetes with known risk factors to derive the risk estimation models, from 15,877 people to inform the uptake of screening and from 17,043 people to inform the health-care resource-usage costs. Two stratification models were developed: one using only results from previous screening events and one using previous screening and some commonly available GP data. Both models were capable of differentiating groups at low and high risk of development of STDR. The rate of progression to STDR was 5 per 1000 person-years (PYs) in the lowest decile of risk and 75 per 1000 PYs in the highest decile. In the absence of personalised risk stratification, the most cost-effective screening interval was to screen all patients every 3 years, with a 46% probability of this being cost-effective at a £30,000 per QALY threshold. Using either risk stratification models, screening patients at low risk every 5 years was the most cost-effective option, with a probability of 99-100% at a £30,000 per QALY threshold. For the medium-risk groups screening every 3 years had a probability of 43 –48% while screening high-risk groups every 2 years was cost-effective with a probability of 55–59%.

Conclusions:

The study found that annual screening of all patients for STDR was not cost-effective. Screening this entire cohort every 3 years was most likely to be cost-effective. When personalised intervals are applied, screening those in our low-risk groups every 5 years was found to be cost-effective. Screening high-risk groups every 2 years further improved the cost-effectiveness of the programme. There was considerable uncertainty in the estimated incremental costs and in the incremental QALYs, particularly with regard to implications of an increasing proportion of maculopathy cases receiving intravitreal injection rather than laser treatment. Future work should focus on improving the understanding of risk, validating in further populations and investigating quality issues in imaging and assessment including the potential for automated image grading.

Study registration:

Integrated Research Application System project number 118959.

Funding details:

The National Institute for Health Research Health Technology Assessment programme.

Contents

Article history

The research reported in this issue of the journal was funded by the HTA programme as project number 10/66/01. The contractual start date was in May 2012. The draft report began editorial review in December 2014 and was accepted for publication in May 2015. The authors have been wholly responsible for all data collection, analysis and interpretation, and for writing up their work. The HTA editors and publisher have tried to ensure the accuracy of the authors’ report and would like to thank the reviewers for their constructive comments on the draft document. However, they do not accept liability for damages or losses arising from material published in this report.

Declared competing interests of authors

Peter Scanlon has received fees from Bayer Plc (Newbury, UK), Allergan Ltd (Marlow, UK), Roche (F. Hoffmann-La Roche Ltd, Basel, Switzerland) and Boots Opticians Ltd (Nottingham, UK) for consultancy work or advisory board participation and part of his salary is supported by the NHS Diabetic Eye Screening Programme in Public Health England. Stephen Aldington has part of his salary supported by the NHS Diabetic Eye Screening Programme in Public Health England. Sobha Sivaprasad has received fees from Novartis Pharmaceuticals UK Ltd (Frimley, UK), Bayer, Allergan and Roche for travel grants and research grants and advisory board participation.

Copyright © Queen’s Printer and Controller of HMSO 2015. This work was produced by Scanlon et al. under the terms of a commissioning contract issued by the Secretary of State for Health. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK316349DOI: 10.3310/hta19740

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