Assessment of hip involvement in patients with ankylosing spondylitis: reliability and validity of the Hip Inflammation MRI Scoring System

BACKGROUND: This study aimed to test the reliability and validity of the Hip Inflammation MRI Scoring System (HIMRISS) in assessing hip involvement of AS patients with AS at different stages of the bath ankylosing spondylitis radiology index (BASRI-hip) scoring system. METHODS: Fifty-two outpatients with ankylosing spondylitis (AS) were included in this study. The subjects’ data includes demographics, clinical characteristics, disease activity score, and functional index. Based on the Harris hip scoring (HHS) of involved hip and BASRI-hip score, we devided these patients into no hip involvement group((HHS ≥ 80 and BASRI ≤ 1) (Group A), mild hip involvement subgroup (BASRI = 2 or BASRI ≤ 1 and HHS ≤ 79) (Group B), and moderate to advanced hip involvement subgroup (BASRI ≥ 3) (Group C). Data was analyzed statistically by SPSS software. RESULTS: In total of 44 patients (88 hips), group A consisted of 21 hips, group B consisted of 42 hips and group C consisted of 25 hips. The test–retest intraclass correlation coefficients (ICCs) in four raters were 0.955 ~ 0.977 and interrater ICC was 0.993. HIMRISS correlated moderately with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (r = 0.540, p < 0.001), the Bath ankylosing spondylitis functional index (BASFI) (r = 0.540, p < 0.001), the Bath Ankylosing Spondylitis Functional Index (BASFI) (r = 0.581, p < 0.001), ASDAS-ESR (r = 0.604, p < 0.001), and Ankylosing Spondylitis Disease Activity Score (ASDAS)-C reactive protein (CRP) (r = 0.575, p < 0.001). HIMRISS in groups B and C was significantly higher than that in group A: 29.38 (17.00, 40.94) vs. 14.50 (11.38, 22.25), p = 0.009; 38 (31.13, 64.38) vs 14.50 (11.38, 22.25), p < 0.001. CONCLUSIONS: HIMRISS applied to patients with AS demonstrated a satisfactory reliability, meaning it is a reliable quantitive assessment tool for evaluating early hip involvement in patients with AS.