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Validity and reliability of the Assessment of Spondyloarthritis International Society Health Index in English‐speaking patients with axial spondyloarthritis in Singapore
Author(s) -
Kwan Yu Heng,
Aw Fang Fang,
Fong Warren,
Phang Jie Kie,
Kiltz Uta,
Lim Ka Keat,
Chew Eng Hui,
Lui Nai Lee,
Tan Chuen Seng,
Thumboo Julian,
Østbye Truls,
Leung Ying Ying
Publication year - 2019
Publication title -
international journal of rheumatic diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.795
H-Index - 41
eISSN - 1756-185X
pISSN - 1756-1841
DOI - 10.1111/1756-185x.13640
Subject(s) - cronbach's alpha , medicine , convergent validity , construct validity , intraclass correlation , face validity , physical therapy , discriminant validity , clinical psychology , psychometrics , internal consistency
Objectives To assess the validity and reliability of the Assessment of Spondyloarthritis International Society Health Index (ASAS HI) among patients with axial spondyloarthritis (axSpA) in Singapore. Methods We collected data from English‐speaking patients with axSpA seen at a dedicated axSpA clinic in a Singapore tertiary referral hospital from 2017 to 2018. Face validity of the English version of ASAS HI was assessed through cognitive debriefing interviews (CDIs). Structural validity was assessed with confirmatory factor analysis. Convergent construct validity was assessed with 12 a priori hypotheses about the magnitude and direction of correlations between the ASAS HI summary score and other patient‐reported outcome measures. Internal consistency was assessed using Cronbach's alpha. Test‐retest reliability was assessed by intraclass correlation coefficient (ICC). Measurement error was assessed by analyzing smallest detectable change (SDC). Results Ten patients (age range 22‐46 years, 50% male) participated in CDIs and face validity was supported. Among 108 patients (median age: 37 [21‐77], 80.6% males), unidimensionality was confirmed (comparative fit index = 0.960, Tucker‐Lewis Index = 0.952, root mean square error of approximation = 0.038, standardized root mean residuals = 0.068, model Chi‐square test P = 0.1251) in the 17‐item ASAS HI. The ASAS HI showed good internal consistency of 0.83 and excellent test‐retest reliability (ICC = 0.95; 95% CI 0.91‐0.98) when baseline was compared with week 2. SDC was 1.02. Convergent validity was supported as hypotheses were confirmed in 100% of the results. Conclusions This study supports the ASAS HI as a valid and reliable measure of health status for use in patients with axSpA in Singapore.