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.