Comparison of generic versus disease-specific measures of functional impairment in patients with cataract

The increased demand for health status measures in evaluating medical interventions has increased the importance of clarifying when to use generic versus disease-specific health status measures. The authors compared the performance of a well known generic health status measure, the Sickness Impact Profile (SIP), and a disease-specific measure of functional impairment related to vision (the VF-14) in detecting functional impairment in 426 cataract patients before and at 12 months after first eye cataract surgery. Using analysis of covariance models, the associations were assessed between the SIP and VF-14 and four criterion variables--patient ratings of trouble and satisfaction with their vision and overall health, and best corrected visual acuity--after controlling for patient age and medical comorbidities. Preoperative patient ratings of trouble and satisfaction with vision were significantly associated with VF-14 scores (P < 0.001), but not with SIP scores. Preoperative visual acuity in the better eye was significantly associated with both VF-14 and SIP scores (P < 0.001). Patient general health ratings were significantly associated with SIP scores (P < 0.001), but not with VF-14 scores. Postoperative changes in patient ratings of their vision and in visual acuity were significantly associated with changes in VF-14 scores (P < 0.05), but not with changes in SIP scores. Changes in patient ratings of overall health were significantly associated with changes in SIP scores (P < 0.01), but not with changes in VF-14 scores. In patients undergoing cataract surgery, a disease-specific health status measure is more sensitive to preoperative functional impairment related to vision, and to change in functional impairment after cataract surgery, than is a generic health status measure.