Internal consistency and item-total correlation of patient-reported outcome instruments and hemophilia joint health score v2.1 in US adult people with hemophilia: results from the Pain, Functional Impairment, and Quality of life (P-FiQ) study

Background The Pain, Functional Impairment, and Quality of Life study was an observational, cross-sectional assessment of the impact of pain on functional impairment and quality of life in adult people with hemophilia (PWH) of any severity in the USA who experience joint pain and/or bleeding. Objective To assess internal consistency (IC) and item-total correlation (ITC) of assessment tools used in the Pain, Functional Impairment, and Quality of Life study. Methods Participants completed 5 patient-reported outcome instruments (EQ-5D-5L with visual analog scale, Brief Pain Inventory v2 Short Form [BPI], International Physical Activity Questionnaire [IPAQ], Short Form 36 Health Survey v2 [SF-36v2], and Hemophilia Activities List [HAL]) and underwent an optional physiotherapist-administered musculoskeletal exam (Hemophilia Joint Health Score v2.1) during routine visits. Reliability assessment included IC and ITC of each instrument. Results A total of 381 adult PWH (median age, 34 years) were enrolled. Participants were predominantly white/non-Hispanic (69.2%); 75% had congenital hemophilia A, and 70.5% had severe hemophilia. A total of 310 subjects reported bleeding within the past 6 months (mean [SD] number of bleeds, 7.1 [13.00]). IC was generally high across the instruments employed (Cronbach's alpha 0.79-0.98) with the exception of HAL use of transportation (0.58) and IPAQ total physical activity (0.51). ITC was high (Pearson's product-moment correlation coefficient >0.20) for all items except the "vigorous intensity activities" item of IPAQ, which was applicable to less than one-third of participants. The ITCs were generally highest in domains/scores that measured the functional consequences of hemophilic arthropathy on mobility and pain. Conclusion The demonstrated reliability (IC/ITC) of the patient-reported outcome instruments and Hemophilia Joint Health Score v2.1 support a role for these instruments in evaluating adult PWH in US clinical and research settings.