Background The measurement properties of the ASAS Health Index (ASAS HI) which has been developed to measure health and functioning of patients with spondyloarthritis (SpA) have been evaluated in a cohort study. Its association with structural changes has not been examined to date.
Objectives To investigate the relationship between clincial data, function and health as assessed by the ASAS HI in patients with axial SpA (axSpA) and to study the influence of structural spinal changes on this instrument.
Methods Patients fullfilling ASAS classification criteria for axSpA were recruited prospectively. Information was collected on clinical assessments (ASAS HI, NRS pain, BASDAI, ASDAS, BASFI, BASMI), laboratory parameters and spinal x-rays. Images were scored using mSASSS by two independent readers. The relationship between ASAS HI and other health outcomes was evaluated by Spearman correlation.
Results A total of 150 patients (57 nr-axSpA and 93 AS patients) were included: 68.7% male, mean (SD) age 46.4 (14.1), symptom duration 18.7 (13.5) and diagnosis since 11.4 (11.8) years, and HLA-B27 positive in 82.0%. Values of clinical assessments were ASAS HI 7.4 (4.1), BASDAI 4.7 (2.3), ASDAS 2.7 (1.1), BASMI 3.3 (1.8), pain 5.7 (2.7), and BASFI 4.7 (2.6). Elevated CRP levels were found in 34.8% of the patients. Radiographs of the sacroiliac (SI) joint and the spine were available in 138 patients, 38.0% of which had syndesmophytes and 7.5% had a bamboo spine. The median (IQR) mSASSS value was 4.3 (IQR 1.0–22.1) in AS und 0.2 (IQR 0.0–1.4) in nr-axSpA patients. Patients received a treatment with NSAIDs (62.7%), DMARDs (20.9%) and/or biologics (49.4%). Significant correlation of ASAS HI was found for BASFI (r=0.8), BASDAI (r=0.7), ASDAS (r=0.5) and BASMI (r=0.5, and, all p<0.05). No correlations were found for ASAS HI and radiographic damage (mSASSS r=0.2, occurrence of syndesmophytes r=0.01, occurrence of bamboo spine r=0.2) and CRP levels (r=0.07). Stratifying patients by symptom duration (cut-off 3 years) did not affect these results.
Conclusions Established measures of function and spinal mobility correlate well with the ASAS HI in patients with axSpA. The influence of structural changes as measured by mSASSS on the ASAS HI was limited in this study, probably due to relatively low mSASSS scores at baseline,. Further study in more and more severe patients is needed to study the association of physical activity, spinal mobility, function and radiographic damage in axSpA.
Disclosure of Interest None declared