Systematic review of the diagnostic accuracy of the single, two and three field digital retinal photography for screening diabetic retinopathy.
BACKGROUND
Regular eye examinations are important to aid in early detection of diabetic retinopathy. Screening methods include ophthalmoscopy, retinal photography and variations of both. Digital retinal photography (DRP) is being increasingly adopted. The gold standard is to photograph seven visual fields, in practice, however, fewer fields such as single, two or three fields are used, to reduce cost and time. There is no existing review comparing the diagnostic accuracy of the single, two and three-field DRP.


OBJECTIVE
To perform a systematic review of the diagnostic accuracy of the single, two and three field DRP for screening diabetic retinopathy.


METHODS
All patients with diabetes mellitus who attended an eye screening were included. Studies which include digital retinal imaging techniques that capture single, two or three visual images were considered.To be included, studies must have compared the technique to a reference standard, either the seven-field stereoscopic fundus photography (7SF) or indirect ophthalmoscopy.


METHODS
The main outcomes were sensitivity and specificity of the screening technique.


METHODS
Search was carried out, for the time period 1985 to December 2008, for full text papers and conference abstracts.


METHODS
Methodological quality of included studies was assessed by two reviewers using an adapted version of the critical appraisal tool for diagnostic studies developed by the Critical Appraisal Skills Programme at the Public Health Resource Unit.


METHODS
Data from included studies were extracted using a modified JBI data extraction tool.


RESULTS
Studies were grouped by the reference standard used and summarised using tabular and narrative formats.


RESULTS
Twenty-two primary studies met the review criteria. Fifteen studies used a single field, five applied two-field and seven applied three-field. There was great heterogeneity among the studies. Using 7SF as a reference standard, the sensitivity (for detecting any retinopathy) of the single, two and three fields ranged from: 66%-87%, 86%-98%, and 66%-98%. For indirect ophthalmoscopy, sensitivity ranged from 38%-100%, 83%-97%, and 90%-97%. The corresponding specificity for 7SF was 45%-96%, 78%-95%, 72%-86%; for indirect ophthalmoscopy was 47%-100%, 79%-100%, 90%-98%. Five studies comparing more than one field type had a general trend of higher sensitivity and lower specificity with increasing number of fields. Pupil dilation led to a lower proportion of ungradeable images.


CONCLUSIONS
The review findings are limited by the heterogeneity between studies and the number of studies comparing more than one screening type. Evidence for the optimal number of screening fields is not conclusive.


CONCLUSIONS
Until further research is available for stronger comparisons to be made, single field DRP would be the option requiring less time and lower costs. Dilation should be applied to reduce ungradeable images. Older age, smaller pupil size, and presence of cataract are associated with ungradeable images.


CONCLUSIONS
There is a strong recommendation for field specialists to achieve consensus on DRP methods including a standard scale for grading diabetic retinopathy and common threshold for referrable retinopathy. Future studies should consider following the Standards for Reporting of Diagnostic Accuracy (STARD). A prospective study comparing the single, two and three fields, with and without dilation will provide the required evidence for optimal number of fields.
1. Research Analyst, Health Services & Outcomes Research National Healthcare Group, 6 Commonwealth Lane #04 01/02 GMTI Building, Singapore 149547. 2. National Healthcare Group HSOR Collaborating Centre for Evidence Based health Services management: A Collaborating Centre of The Joanna Briggs Institute.
Anusha
A
Govinda
Robyn
R
de Verteuil