Effects of patient and disease characteristics on global functioning in patients with axial spondyloarthritis in routine care

Abstract

BackgroundThe ASAS Health Index (ASAS HI) was developed to assess global functioning in patients with axial spondyloarthritis (axSpA). Influencing factors have not been studied to date, especially the influence of inflammation and structural changes in the spine has remained unclear to date. ObjectiveTo find out whether and to what degree do axial inflammation, radiographic damage and other clinical features influence global functioning of patients with axSpA. MethodsPatient reported outcomes (ASAS HI, pain, BASDAI, BASFI, EQ-5D and SF-36) were assessed, spinal mobility by BASMI and depression by SF-36 scores. Axial inflammation was quantified using the MRI Berlin score and structural damage as detected by conventional radiographs by the modified Stokes AS Spinal Score (mSASSS). Correlation and regression analyses were performed to analyze the association between global functioning and other variables. ResultsA total of 191 axSpA patients with different degrees of global functioning and disease activity was included, 60.2% had r-axSpA. Syndesmophytes were found in 38.5% of patients - with a median mSASSS score of 3.8 (IQR 1.0-18.7) in r-axSpA and 0.0 (IQR 0.0-1.2) in nr-axSpA patients. The mean MRI score was 2.3 (IQR 0.5-7.6). ASAS HI values correlated significantly with BASMI, BASDAI, BASFI, BMI and MRI scores. However, no significant correlation was found for mSASSS and CRP. Regression analyses revealed that global functioning was significantly influenced by disease activity, physical function, obesity and depression but not by structural damage or spinal inflammation as detected MRI. ConclusionsOur study shows that global functioning is strongly associated with physical function, body weight and depression in patients with axSpA but not with spinal inflammation and structural damage. This may be explained by the relatively low mSASSS of these well treated patients.