Validation of the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0 in English- and Chinese-speaking patients in a multi-ethnic Singapore systemic sclerosis cohort.

Abstract

The aim of this study was to (1) translate the Gastrointestinal Tract Instrument (GIT) 2.0 from English to Chinese and (2) validate both versions in a multi-ethnic systemic sclerosis cohort in Singapore (SCORE). The English GIT2.0 was translated to Chinese using a standard forward-backward translation approach. Psychometric evaluation of the GIT2.0 included internal consistency reliability (using Cronbach's alpha), test-retest reliability (using intra-class correlation coefficient (ICC)), scale level factor analysis, and construct validity (using Spearman correlation) against the modified Scleroderma Health Assessment Questionnaire (S-HAQ) and the SF-36 v2. Most of the patients were females (88.6%) and Chinese (78.2%), with mean (SD) age of 51.0 (13.0) years and median disease duration of 4.5years. We administered English (n=146) and Chinese (n=74) GIT2.0. The mean (SD) total GIT score was 0.29 (0.37). There was good internal consistency (Cronbach's alpha >0.70 for all subscales) and good test-retest reliability for the scale and all subscales (ICC 0.71-0.92) except for "diarrhoea" (ICC=0.54). Our hypothesised a priori construct validity was supported by moderate correlations between the total GIT score and S-HAQ GI subscale (r=0.446), and the social functioning subscale and SF36v2 role-social domain (r=0.337), and weak-to-moderate correlation between the emotional subscale and SF-36v2 role-emotional (r=0.295) and mental health (r=0.298) domains and mental component summary (r=0.356). Exploratory factor analysis of the seven subscales yielded a two-factor solution explaining 69.63% of the total variance. This study provides evidence for the reliability and validity of the English and Chinese GIT2.0 to be used in Singapore for research and routine practice.