Background: Expert recommendations propose the WHO Disability Assessment Schedule (WHODAS) 2.0 as a core outcome measure in surgical studies, yet data on its long-term measurement properties remain limited. These were evaluated in a secondary analysis of the Measurement of Exercise Tolerance before Surgery (METS) prospective cohort.
Methods: Participants were adults (40 years of age or older) who underwent inpatient non-cardiac surgery. The 12-item WHODAS and EQ-5DTM-3L questionnaires were administered preoperatively (in person) and 1 year postoperatively (by telephone). Responsiveness was characterized using standardized response means (SRMs) and correlation coefficients between change scores. Construct validity was evaluated using correlation coefficients between 1-year scores and comparisons of WHODAS scores across clinically relevant subgroups.
Results: The analysis included 546 patients. There was moderate correlation between changes in WHODAS and various EQ-5DTM subscales. The strongest correlation was between changes in WHODAS and changes in the functional domains of the EQ-5D-3L-for example, mobility (Spearman's rho 0.40, 95 per cent confidence interval [c.i.] 0.32 to 0.48) and usual activities (rho 0.45, 95 per cent c.i. 0.30 to 0.52). When compared across quartiles of EQ-5D index change, median WHODAS scores followed expected patterns of change. In subgroups with expected functional status changes, the WHODAS SRMs ranged from 'small' to 'large' in the expected directions of change. At 1 year, the WHODAS demonstrated convergence with the EQ-5D-3L functional domains, and good discrimination between patients with expected differences in functional status.
Conclusion: The WHODAS questionnaire has construct validity and responsiveness as a measure of functional status at 1 year after major surgery.
Surgery can have a long-lasting impact on a person’s ‘functional status’, which is their ability to carry out routine functions of daily living (e.g. work, chores, and social activity). International societies now recommend that functional status be routinely measured in research studies of patients having surgery. A potential instrument to measure functional status in patients having surgery is the WHO Disability Assessment Schedule (WHODAS) 2.0. The WHODAS 2.0 was originally designed to measure function and disability in a general population (i.e. not patients having surgery). In this study, we show that the WHODAS 2.0 has acceptable performance when measuring functional status in patients having surgery.
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