Ronald J. Lorimor

Screening for Diabetic Retinopathy: The wide-angle retinal camera

OBJECTIVE— To define the test characteristics of four methods of screening for diabetic retinopathy. RESEARCH DESIGN AND METHODS— Four screening methods (an exam by an ophthalmologist through dilated pupils using direct and indirect ophthalmoscopy, an exam by a physicians assistant through dilated pupils using direct ophthalmoscopy, a single 45° retinal photograph without pharmacological dilation, and a set of three dilated 45° retinal photographs) were compared with a reference standard of stereoscopic 30° retinal photographs of seven standard fields read by a central reading center. Sensitivity, specificity, and positive and negative likelihood ratios were calculated after dichotomizing the retinopathy levels into none and mild nonproliferative versus moderate to severe nonproliferative and proliferative. Two sites were used. All patients with diabetes in a VA hospital outpatient clinic between June 1988 and May 1989 were asked to participate. Patients with diabetes identified from a laboratory list of elevated serum glucose values were recruited from a DOD medical center. RESULTS— The subjects (352) had complete exams excluding the exam by the physicians assistant that was added later. The sensitivities, specificities, and positive and negative likelihood ratios are as follows: ophthalmologist 0.33, 0.99, 72, 0.67; photographs without pharmacological dilation 0.61, 0.85, 4.1, 0.46; dilated photographs 0.81, 0.97, 24, 0.19; and physicians assistant 0.14, 0.99, 12, 0.87. CONCLUSIONS— Fundus photographs taken by the 45° camera through pharmacologically dilated pupils and read by trained readers perform as well as ophthalmologists for detecting diabetic retinopathy. Physician extenders can effectively perform the photography with minimal training but would require more training to perform adequate eye exams. In this older population, many patients did not obtain adequate nonpharmacological dilation for use of the 45° camera.

Cost-effectiveness of alternative methods for diabetic retinopathy screening

OBJECTIVE To assess from the perspectives of a government delivery system and patients, the cost-effectiveness of the 45-degrees retinal camera compared to the standard ophthalmologists exam and an ophthalmic exam by a physicians assistant or nurse practitioner technician, for detecting nonproliferative and proliferative diabetic retinopathy. RESEARCH DESIGN AND METHODS Comparison of 45-degrees fundus photographs with and without pharmacological pupil dilation taken by technicians and interpreted by experts, direct and indirect ophthalmoscopy by ophthalmologists, and direct ophthalmoscopy by technicians with seven-field stereoscopic fundus photography (reference standard). Costs were estimated from market prices and actual resource use. The study included 352 patients attending outpatient diabetes and general-medicine clinics at VA and DOD facilities. RESULTS Medical system costs per true positive were: 45-degrees photos with dilation,

Analysis of Complex Sample Survey Data: Problems and Strategies

295; 45-degrees photos without dilation,

Estimates of the demand for health: Males in the pre-retirement years

378; ophthalmologist,

The effects of response bias on sex differences in a psychiatric population.

390; and technician,

Variability in food consumption patterns of adults in the U.S. population

794. Patient costs per true positive were: 45-degrees photos with dilation,

SEX DIFFERENCES IN PERCEPTION OF LIFE EVENTS USING SELF-WEIGHTS

139; 45-degrees photos without dilation,

Analyzing Complex Survey Data

171; ophthalmologist,

Terminally ill cancer patients. Their most important concerns.

306; and technician,

How Children Spend Their Time: A Sample Survey for Use in Exposure and Risk Assessments

1009. Cost-effectiveness is sensitive to program size due to high fixed cost of the camera methods but not to prevalence. Cost-effectiveness of the technician exam is strongly affected by its sensitivity. CONCLUSIONS Primary-care screening with retinal photographs through pharmacologically dilated pupils for diabetic retinopathy is an appropriate and cost-effective alternative to screening by an ophthalmologist in this setting. Ophthalmologists are scarce, primary-care physicians are extremely busy, and large clinics allow fixed equipment costs to be spread across many patients.