Colour vision testing for diabetic retinopathy: a systematic review of diagnostic accuracy and economic evaluation

To determine the diagnostic performance and cost-effectiveness of colour vision testing (CVT) to identify and monitor the progression of diabetic retinopathy (DR).

Major electronic databases including MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Database of Systematic Reviews were searched from inception to September 2008.

A systematic review of the evidence was carried out according to standard methods. An online survey of National Screening Programme for Diabetic Retinopathy (NSPDR) clinical leads and programme managers assessed the diagnostic tools used routinely by local centres and their views on future research priorities. A decision tree and Markov model was developed to estimate the incremental costs and effects of adding CVT to the current NSPDR.

In total, 25 studies on CVT met the inclusion criteria for the review, including 18 presenting 2 x 2 diagnostic accuracy data. The quality of studies and reporting was generally poor. Automated or computerised CVTs reported variable sensitivities (63-97%) and specificities (71-95%). One study reported good diagnostic accuracy estimates for computerised CVT plus retinal photography for detection of sight-threatening DR, but it included few cases of retinopathy in total. Results for pseudoisochromatic plates, anomaloscopes and colour arrangement tests were largely inadequate for DR screening, with Youden indices (sensitivity + specificity - 100%) close to zero. No studies were located that addressed patient preferences relating to CVT for DR. Retinal photography is universally employed as the primary method for retinal screening by centres responding to the online survey; none used CVT. The review of the economic evaluation literature found no previous studies describing the cost and effects of any type of CVT. Our economic evaluation suggested that adding CVT to the current national screening programme could be cost-effective if it adequately increases sensitivity and is relatively inexpensive. The deterministic base-case analysis indicated that the cost per quality-adjusted life-year gained may be 6364 pounds and 12,432 pounds for type 1 and type 2 diabetes respectively. However, probabilistic sensitivity analysis highlighted the substantial probability that CVT is not diagnostically accurate enough to be either an effective or a cost-effective addition to current screening methods. The results of the economic model should be treated with caution as the model is based on only one small study.

There is insufficient evidence to support the use of CVT alone, or in combination with retinal photography, as a method for screening for retinopathy in patients with diabetes. Better quality diagnostic accuracy studies directly comparing the incremental value of CVT in addition to retinal photography are needed before drawing conclusions on cost-effectiveness. The most frequently cited preference for future research was the use of optical coherence tomography for the detection of clinically significant macular oedema.