Background Diseases with inflammation and damage of joints lead to tissue degradation and YKL-40 may be as a marker of this fact. Ankylosing spondylitis (AS) exhibit higher levels of plasma YKL-40 compared with healthy controls. Spine and sacroiliacs joints are the main target of inflammation in AS and structural damage led to limitation of mobility and disability of patients.
Objectives To evaluate YKL-40 serum levels in relation with structural damage and metrology in a longitudinal observational cohort of anti-TNF naïve AS patients.
Methods Data from patients with diagnoses of AS (modified NY criteria) included demographic characteristics (age, gender, disease duration, body mass index-BMI), Metrology (cervical rotation, occiput to wall distance, chest expansion, lumbar lateral flexion, modified Schober's, finger to floor distance and intermalleolar distance), BASDAI and BASFI scores, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Radiographs of these patients were obtained and scored according to the Bath AS Radiology Index-spine (BASRI-s) at baseline (BASRI-spine, range 2-12; sacroiliac joints, AP and lateral views of lumbar spine, lateral view of cervical spine). Serum levels of YKL-40 were determined by ELISA (ng/ml) in blood samples at the entry in the cohort. Data are presented as mean (standard deviation). Correlations were assessed using the Spearman's rho correlation coefficient. P-values <0.05 were considered statistically significant.
Results Data were available on 100 patients, 82 male (82.0%), mean of age 48.7 (12.9) years, disease duration 12.5 (8.9) years and BASRI-s score 7.4 (3.5). Serum level mean (SD) of YKL-40 obtained from 86 patients was 125.9 (89.9) and had correlation with age (r 0.54; p<0.0001), disease duration (r 0.27; p 0.011), BMI (r 0.26; p 0.017), BASFI (r 0.41; p<0.0001), cervical rotation (p 0.002), occiput-to-wall distance (r 0.28; p 0.007), chest expansion (r -0.33; p 0.005), modified Schober test (r -0.30; p 0.017), finger-to-floor distance (r 0.28; p 0.008), intermalleolar distance (r -0.40; p<0.0001) and BASRI-s (r 0.38; p<0.0001). Differences had not statistical significance with regard to lumbar lateral flexion (r -0.24; p 0.059) and not correlation was seen with gender (p 0.387), ESR (r 0.13; p 0.223), CRP (r -0.13; p 0.235) and BASDAI (r 0.08; p 0.425). Moreover, BASRI-s correlated with disease duration (r 0.51; p<0.0001) and with age (r 0.52; p<0.0001).
Conclusions In our study serum levels of YKL-40 correlated with worsening of functional ability (metrology and BASFI) and axial structural damage (BASRI-spine) like disease progression in ankylosing spondylitis.
Pedersen SJ et al. Radiographic progression is associated with resolution of systemic inflammation in patients with axial spondylarthritis treated with tumor necrosis factor α inhibitors: a study of radiographic progression, inflammation on magnetic resonance imaging, and circulating biomarkers of inflammation, angiogenesis, and cartilage and bone turnover. Arthritis Rheum. 2011 Dec;63(12):3789-800. doi: 10.1002/art.30627.
Disclosure of Interest None declared