POS1472-HPR CONSTRUCT VALIDITY OF THE PROMIS PHYSICAL FUNCTION 10-ITEM SHORT FORM IN PATIENTS WITH INFLAMMATORY RHEUMATIC DISEASES AND SEVERE LIMITATIONS IN PHYSICAL FUNCTIONING

Abstract

BackgroundPhysical functioning in patients with inflammatory arthritis (IA) can be severely affected and is often measured using the disease-specific questionnaires Health Assessment Questionnaire-Disability Index (HAQ-DI) or Bath Ankylosing Spondylitis Functional Index (BASFI). Also, the Patient Reported Outcome Measurement Information System (PROMIS) Physical Function Item Bank1 has been increasingly used. This is a generic instrument to assess physical functioning and compare health status across conditions. Several short forms can be derived, including the PROMIS PF 10-Item Short Form (PROMIS PF-10). To date, experience with this PROMIS PF-10 in research with IA is limited and more insight is needed in its construct validity in specific IA populations.ObjectivesTo assess the construct validity of the PROMIS PF-10 in patients with rheumatoid arthritis (RA) or axial spondyloarthritis (axSpA) and severe limitations in physical functioning.MethodsBaseline data from patients with RA or axSpA and severe limitations in physical functioning participating in two randomized controlled trials on the effectiveness of longstanding physical therapy2 were used. Patients completed the PROMIS PF-10 (score range 13.5-61.9 worst-best, standardized to the Dutch population) and several measures of physical functioning and quality of life: i.e. the 36-item Short Form Health Survey (SF-36) (Physical and Mental Component summary Scores (PCS and MCS) were calculated), the EuroQol 5-dimensions 5-levels (EQ5D5L; index and VAS) and the 6 Minute Walk Test (6MWT). In addition, RA patients completed the HAQ-DI and axSpA patients the BASFI. Spearman rho correlation coefficients were computed between the PROMIS PF-10 and the other measures. Correlations were considered 0.3<r<0.5 weak, 0.5 <r<0.75 moderate to good, r >0.75 good to excellent. The PROMIS PF-10 was expected to correlate moderately to good with instruments measuring physical functioning and weak with other instruments (e.g. SF-36 MCS). All analyses were stratified for RA and axSpA.ResultsData from 181 patients with RA and 139 with axSpA (92% and 48% female, mean (SD) age 59 (13.1) and 54 (11.4) years, respectively) were analyzed. The mean score of the measures of physical functioning and quality of life are summarized in the Table 1. The PROMIS PF-10 correlated moderately to good with HAQ-DI, BASFI, SF-36 PCS and EQ5D5L-index (Spearman r >0.5, all p-values <0.001). The PROMIS PF-10 correlated weak with the 6MWT, EQ-VAS and the SF-36 MCS (Spearman r <0.5).Table 1.Mean score and Spearman r correlation coefficients of PROMIS PF-10 with measures of physical functioning and quality of lifePROMIS PF-10HAQ-DI (RA) BASFI (axSpA)SF-36 PCSSF-36 MCSEQ5D5L indexEQ-VAS6MWTRA Mean(SD)34.1 (5.0)1.6 (0.5)39.4 (19.7)46.8 (12.0)0.5 (0.3)56.4 (18.7)300 (100)Spearman r--0.724*0.611*0.1010.617*0.450*0.469*AxSpA Mean(SD)35.4 (4.2)6.2 (1.8)44.4 (17.6)45.5 (11.6)0.5 (0.3)54.5 (19.0)390 (108)Spearman r--0.686*0.539*-0.0140.598*0.438*0.434**Correlation is significant at <0.001 levelConclusionThe moderately to good correlations of the PROMIS PF-10 with measures of physical functioning support the construct validity in RA and axSpA patients with severe limitations in physical functioning. However, the correlation of the quality of life questionnaire EQ5D5L was also moderately to good. Future research is needed to better understand this relatively high correlation. Also clinimetric properties (responsiveness to change and ability to discriminate between intervention and control conditions) in this population should be determined in future.