Establishing ongoing quality assurance in a retinal screening programme

To establish a clinically efficient, cost-effective quality assurance programme as part of a routine retinopathy screening service.

The operation of a quality assurance system as part of an ongoing retinal screening service is described. A random selection of 12% of images of all people reported to have retinopathy and of 2% reported to have no retinopathy are re-graded by a consultant ophthalmologist. Entry of the two sets of data into a purpose-designed excel spreadsheet allows automated calculation of sensitivity and specificity.

The results of quality assurance from August 2001 to July 2003 are reported. Out of 8351 screening episodes, 498 were re-examined. Of the 62 cases identified by the ophthalmologist as having referable retinopathy, four false negatives for detection were identified. Three of these had been assigned to early re-screening by the retinal screener but were still regarded as false negative by the parameters of the quality assurance system. The sensitivity and specificity for detection of sight-threatening retinopathy were 93.5% (95% CI = 84.3-98.2%) and 97.8% (95% CI = 95.8-98.9%), respectively.

A robust and cost-effective system has been developed to allow monitoring of performance of routine retinal screening which may be extended to meet current national recommendations.