Known-group validity of patient-reported outcome instruments and hemophilia joint health score v2.1 in US adults with hemophilia: results from the Pain, Functional Impairment, and Quality of life (P-FiQ) study

The Pain, Functional Impairment, and Quality of Life (P-FiQ) study was an observational, cross-sectional assessment of the impact of pain on functional impairment and quality of life in adults with hemophilia in the United States who experience joint pain or bleeding. To describe known-groups validity of assessment tools used in the P-FiQ study. Participants completed 5 patient-reported outcome (PRO) instruments (5-level EuroQoL 5-dimensional questionnaire [EQ-5D-5L] with visual analog scale [VAS], Brief Pain Inventory v2 Short Form [BPI], International Physical Activity Questionnaire [IPAQ], Short-Form Health Survey [SF-36v2], and Hemophilia Activities List [HAL]) and underwent a musculoskeletal examination (Hemophilia Joint Health Score [HJHS]) during a routine clinical visit. P-FiQ enrolled 381 adults with hemophilia (median age, 34 years). Participants were predominantly white/non-Hispanic (69.2%), 75% had congenital hemophilia A, and 70.5% had severe hemophilia. Most (n=310) reported bleeding within the past 6 months (mean [SD] number of bleeds, 7.1 [13.00]). All instruments discriminated between relevant known (site- or self-reported) participant groups. Domains related to pain on EQ-5D-5L, BPI, and SF-36v2 discriminated self-reported pain (acute/chronic/both;