Abstract
BackgroundVisual impairment from diabetic retinopathy (DR) is an increasing global public health concern, which is preventable with screening and early treatment. Digital retinal imaging has become a preferred choice as it enables higher coverage of screening. The aim of this review is to evaluate how different characteristics of the DR screening (DRS) test impact on diagnostic test accuracy (DTA) and its relevance to a low-income setting.MethodsWe conducted a systematic literature search to identify clinic-based studies on DRS using digital retinal imaging of people with DM (PwDM). Summary estimates of different sub-groups were calculated using DTA values weighted according to the sample size. The DTA of each screening method was derived after exclusion of ungradable images and considering the eye as the unit of analysis. The meta-analysis included studies which measured DTA of detecting any level of DR. We also examined the effect on detection from using different combinations of retinal fields, pupil status, index test graders and setting.ResultsSix thousand six hundred forty-six titles and abstracts were retrieved, and data were extracted from 122 potentially eligible full reports. Twenty-six studies were included in the review, and 21 studies, mostly from high-income settings (18/21, 85.7%), were included in the meta-analysis. The highest sensitivity was observed in the mydriatic greater than two field strategy (92%, 95% CI 90–94%). The highest specificity was observed in greater than two field methods (94%, 95% CI 93–96%) where mydriasis did not affect specificity. Overall, there was no difference in sensitivity between non-mydriatic and mydriatic methods (86%, 95% CI 85–87) after exclusion of ungradable images. The highest DTA (sensitivity 90%, 95% CI 88–91%; specificity 95%, 95% CI 94–96%) was observed when screening was delivered at secondary/tertiary level clinics.ConclusionsNon-mydriatic two-field strategy could be a more pragmatic approach in starting DRS programmes for facility-based PwDM in low-income settings, with dilatation of the pupils of those who have ungradable images. There was insufficient evidence in primary studies to draw firm conclusions on how graders’ background influences DTA. Conducting more context-specific DRS validation studies in low-income and non-ophthalmic settings can be recommended.
Highlights
Visual impairment from diabetic retinopathy (DR) is an increasing global public health concern, which is preventable with screening and early treatment
Overall, both mydriatic and non-mydriatic digital imaging methods generate a satisfactory level of sensitivity, i.e. 86% in usual clinical settings, once ungradable images are excluded from analysis
Diagnostic test accuracy for the detection of any level of DR showed that DR screening (DRS) using two fields delivered at non-primary care settings is a feasible approach
Summary
Visual impairment from diabetic retinopathy (DR) is an increasing global public health concern, which is preventable with screening and early treatment. Diabetes mellitus (DM) is one of the most prevalent non-communicable diseases and has significant impacts on health systems [1]. The greatest impact affects low- and middle-income countries (LMIC) (overall increase 69%) due to ageing population, obesity and sedentary life style [3]. This is exacerbated by weak health systems coupled with slow economic development [4]. DR is a leading cause of blindness among the young and middle-aged adults in most of the high-income countries (HIC)
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