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

BACKGROUND: 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. OBJECTIVE: To describe known-groups validity of assessment tools used in the P-FiQ study. PATIENTS AND METHODS: 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. RESULTS: 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; P<0.05), domains related to functional impairment on IPAQ, SF-36v2, and HAL discriminated self-reported functional impairment (restricted/unrestricted; P<0.05), and domains related to mental health on the EQ-5D-5L and SF-36v2 discriminated self-reported anxiety/depression (yes/no; P<0.01). HJHS ankle and global gait domains and global score discriminated self-reported arthritis/bone/joint problems, percentage of lifetime on prophylaxis, current treatment regimen, and hemophilia severity (P<0.01); knee and elbow domains discriminated all of these (P<0.01) except for current treatment regimen. CONCLUSION: All assessment tools demonstrated known-group validity and may have practical applicability in evaluating adults with hemophilia in clinical and research settings in the United States.