Estimation of the misclassification rate of self-reported visual disability.

PURPOSE To estimate the misclassification rate of self-reported visual disabilities in a hospital-based population with known visual impairment. METHODS Subjects (N=570) were recruited among patients aged 50 years and more and classified to three categories of visual impairment level. The questionnaire was administered to consenting patients through a telephone interview. Data collected from questionnaires and medical records were compared regarding severity of visual impairment. Sensitivity and specificity were determined for each question. Predictive ability and misclassification rates were computed for various prevalences. RESULTS Questions related to near and far distance visual acuity with glasses have both a good sensitivity (82.6% and 81.8%) and a good specificity (85.6% and 88.9%) for the presence of severe visual impairment. CONCLUSION The findings allow the determination of the misclassification rate and predictive ability. This could be useful to estimate the prevalence of visual impairment from health surveys.