Quality assurance in screening for sight-threatening diabetic retinopathy

There is a need for continuous evaluation of screening services for diabetic retinopathy against agreed performance standards. We describe a quality assurance programme implemented in Newcastle in January 1999 and report on outcomes at 18 months.

Annual retinal screening is performed using combined retinal photography and direct ophthalmoscopy in two streams. Diabetologists perform screening in the Hospital Screening Programme, which serves patients whose diabetes is managed in specialist clinics, and trained retinal screeners perform screening in the District Screening Programme, which serves patients whose diabetes is managed in the community. Reference standard examination of dilated fundoscopy with a slit-lamp and condensing lens was performed by an ophthalmologist at periodic sessions on consecutive patients attending for screening.

Six hundred and nine (6.4%) of 9468 patients screened underwent reference standard examination. The sensitivity and specificity of detection of sight-threatening diabetic retinopathy (STDR) was 82.5% and 98%, respectively, for the Hospital Screening Programme; 85.7% and 95.7%, respectively, for the District Screening Programme; and 83.3% and 96.8% for both services combined. One hundred and ten (18.1%) of 609 patients audited were referred to ophthalmology as a result of screening, and this led to 16 patients (2.6%) receiving laser photocoagulation for STDR. Reference standard examination identified a further four patients (0.7%) who required laser photocoagulation.

Preliminary data indicate that satisfactory performance standards are being achieved. The National Service Framework for Diabetes requires that all units institute quality assurance for retinal screening, and we report the practical implementation of this in one district.