Assessing functioning in patients with non-specific serious symptoms referred to a diagnostic cancer pathway: reliability of WHODAS 2.0

Background Patients referred to diagnostic cancer pathways due to non-specific serious symptoms often experience disability. Reliable assessment of functioning is therefore essential for identifying rehabilitation needs. This study examined the test–retest reliability and measurement error of the 36-item World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) in this population.Methods A prospective test–retest reliability study conducted at a Danish cancer diagnostic clinic. Adults (≥18 years) completed WHODAS 2.0 at baseline (T0) and one week later (T1). Reliability was assessed using intraclass correlation coefficients (ICCs), and measurement error using the standard error of measurement (SEM), minimal detectable change (MDC) and Bland–Altman analysis.Results A total of 104 patients completed both assessments. The ICC for the total score was 0.87 (95% CI: 0.82–0.91). Domain-level ICCs ranged from 0.76 to 0.86. The SEM was 8.40 points (6% of maximum score), and the MDC was 23.28 points (16%). Bland–Altman’s analysis showed no systematic bias or floor/ceiling effects, although individual variation was observed.Conclusions WHODAS 2.0 demonstrated excellent reliability and acceptable measurement error. The instrument supports physiotherapists in assessing functioning and identifying rehabilitation needs at the group level in diagnostic cancer pathways but should be used cautiously for detecting small individual changes.