Abstract
Background
We identified that there was less evidence on diagnostic test accuracy (DTA) of diabetic retinopathy (DR) screening photographic studies that have used non-ophthalmologist human resources in low and middle-income country (LMIC) settings. This study is the first to assess the DTA of physician graders using hand held digital imaging in Sri Lanka. We aimed to assess DTA of DR screening using a nonmydriatic hand-held digital camera by trained general physicians in a non-ophthalmic setting. This modality will be useful for adaptation in similar settings.
Methods
This study is a validation of a screening intervention. We selected people with diabetes (PwDM) not previously screened or treated for DR, presenting at a tertiary medical clinic in Sri Lanka. Two-field retinal imaging was used to capture fundus images before and after pupil dilatation. The images were captured and graded by two trained, masked independent physician graders. The DTA of different levels of DR was assessed comparing physician’s grading with a retinologist’s clinical examination according to a locally adopted guideline.
Results
Seven hundred eligible PwDM were screened by physician graders. Their mean age was 60.8 years (SD ±10.08) and mean duration of DM was 9.9 years (SD ±8.09). Ungradable image proportion in non-mydriatic imaging was 43.4% (either eye-31.3%, both eyes 12.1%). This decreased to 12.8% (either eye-11.6%, both eyes-1.2%) following pupil dilatation. In comparison to detection of any level of DR, a referable level DR (moderate non-proliferative DR and levels above) showed a higher level of DTA. The sensitivity of the defined referable DR was 88.7% (95% CI 81.7-93.8%) for grader 1 (positive predictive value [PPV] 59.1%) and 92.5% (95% CI 86.4-96.5%) for grader 2 (PPV 68%), using mydriatic imaging, after including ungradable images as screen positives. The specificity was 94.9% (95% CI 93.6-96.0%) for grader 1 (negative predictive value [NPV] 99%) and 96.4% (95% CI 95.3-97.3%) for grader 2 (NPV 99.4%).
Conclusions
The Physicians grading of images from a digital hand-held nonmydriatic camera was effective in identifying referable DR, following pupil dilatation. This could be a feasible alternative modality to the existing opportunistic screening to improve the access and coverage.
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