Test Accuracy and Predicting Outcome

TO THE EDITOR. —In his recent editorial, Dr Guyton1 emphasized the dangers of attending only to the accuracy of a test to assess visual function behind opacities. He indicated a strong concern with mechanisms responsible for overestimates of postoperative acuity (false-positives) and suggested recommendations for future investigations. Although we agree with Dr Guyton's basic points, we would like to suggest a change in his terminology and an expansion of his area of concern.In most scientific and medical literature, a positive test is by convention one that indicates the presence of a disease.2 A false-positive test indicates the presence of a disease when no disease is present. In ophthalmology, poor visual acuity is evidence of visual disease. By analogy, then, if one is evaluating visual function behind a media opacity, a test that predicted poor postoperative visual acuity should be termed a positive test, and a test that