The Hip Disability and Osteoarthritis Outcome Score-Physical Function Shortform Does Not Adequately Represent Physical Functioning in Patients Undergoing Total Hip Arthroplasty

Objectives: A frequently used patient-reported outcome measure for assessing physical functioning in patients with hip problems is the 5-item Hip Disability and Osteoarthritis Outcome Score-Physical Function Shortform (HOOS-PS). Nevertheless, its content validity (whether this instrument adequately reflects the construct of physical functioning) is unknown. This study aimed to assess the content validity of the HOOS-PS. Methods: A quantitative and qualitative research approach was used. Physical functioning was defined as the ability to perform activities that require physical actions, ranging from self-care to more complex activities that require a combination of skills, often within a social context. Patients (n = 51) and experts (n = 25) completed questionnaires regarding the relevance, comprehensiveness, and comprehensibility of the HOOS-PS. Semistructured interviews (n = 5) explored issues identified in the quantitative data in more depth. Thematic content analysis was conducted using a coding frame. Results: One of the 5 items was considered relevant to measure physical functioning. Comprehensiveness was considered insufficient by both patients and experts. Furthermore, comprehensibility was considered inadequate. Several items were found ambiguous or double barreled. Regarding interpretability, floor or ceiling effects were not found. Conclusions: This study showed concerns about the content validity of the HOOS-PS: most items are considered not relevant, the HOOS-PS is considered not comprehensive, and several items are considered not comprehensible. These findings challenge the applicability of the HOOS-PS in clinical practice, research, value-based healthcare, and benchmarking.