Measurement of disability-free survival after surgery.

BACKGROUND Survival and freedom from disability are arguably the most important patient-centered outcomes after surgery, but it is unclear how postoperative disability should be measured. The authors thus evaluated the World Health Organization Disability Assessment Schedule 2.0 in a surgical population. METHODS The authors examined the psychometric properties of World Health Organization Disability Assessment Schedule 2.0 in a diverse cohort of 510 surgical patients. The authors assessed clinical acceptability, validity, reliability, and responsiveness up to 12 months after surgery. RESULTS Criterion and convergent validity of World Health Organization Disability Assessment Schedule 2.0 were supported by good correlation with the 40-item quality of recovery scale at 30 days after surgery (r = -0.70) and at 3, 6, and 12 months after surgery with physical functioning (The Katz index of independence in Activities of Daily Living; r = -0.70, r = -0.60, and rho = -0.47); quality of life (EQ-5D; r = -0.57, -0.60, and -0.52); and pain interference scores (modified Brief Pain Inventory Short Form; r = 0.72, 0.74, and 0.81) (all P < 0.0005). Construct validity was supported by increased hospital stay (6.9 vs. 5.3 days, P = 0.008) and increased day 30 complications (20% vs. 11%, P = 0.042) in patients with new disability. There was excellent internal consistency with Cronbach's α and split-half coefficients greater than 0.90 at all time points (all P < 0.0005). Responsiveness was excellent with effect sizes of 3.4, 3.0, and 1.0 at 3, 6, and 12 months after surgery, respectively. CONCLUSIONS World Health Organization Disability Assessment Schedule 2.0 is a clinically acceptable, valid, reliable, and responsive instrument for measuring postoperative disability in a diverse surgical population. Its use as an endpoint in future perioperative studies can provide outcome data that are meaningful to clinicians and patients alike.