Background Periostin is a secreted extracellular matrix protein expressed in collagen-rich fibrous connective tissues and involved in cell recruitment and adhesion, and could hypothetically be involved in the syndesmophyte formation in AS.

Objectives To compare the periostin serum levels between patients with AS and healthy controls. Also, to look for association of periostin levels with disease activity and radiographic damage, as well as bone formation markers [total Dickkopf-1 (Dkk-1), sclerostin and vascular endothelial growth factor (VEGF)], in patients with AS.

Methods TNF inhibitor naïve patients with AS were recruited, along with sex-, age- and body mass index (BMI)-matched healthy volunteers as controls. Patients and controls with any medication, including disease modifying antirheumatic drugs (DMARDs), glucocorticoids and non steroidal anti-inflammatory drugs (NSAIDs), or disease that could affect bone metabolism were excluded. The Bath AS Disease Activity Index (BASDAI), inflammatory markers [erythrocyte sedimentation rate (ESR, mm/h) and C-reactive protein (CRP, mg/l)], Bath AS Functional Index (BASFI), modified Stroke AS Spine Score (mSASSS) and Bath AS Radiology Index for the spine (BASRI-s) were assessed for each patient. On the mSASSS scoring system, definite radiographic damage was defined as an mSASSS score of ≥2 (appearance at least one syndesmophyte) in at least one vertebral edge of each patient. On the BASRI-s scoring system, extensive radiographic damage (high BASRI-s score) was defined as a grade 3 or 4 on scoring of cervical or lumbar spine. Serum periostin, total Dkk-1, sclerostin and VEGF were measured in both patients and controls.

Results Serum periostin levels were significantly lower in AS patients (n=65) compared to controls (n=36) (234.4±7.5 pg/ml vs. 291.4±8.3 pg/ml, respectively). All ESR (normal/elevated), CRP (normal/elevated), BASDAI (low/high) and radiographic damage (present syndesmophytes/not, or low/high BASRI-s) subgroups of AS patients had significantly lower periostin levels when compared with controls. Periostin levels were significantly higher in AS patients with elevated CRP (p=0.005), high BASDAI (p=0.014) and low BASRI-s (p=0.033), compared to those with normal CRP, low BASDAI and high BASRI-s respectively. Furthermore, periostin serum levels were correlated with BMI (r= -0.304, p=0.014), ESR (r=0.395, p=0.001), CRP (r=0.413, p=0.001), BASRI-s (r= -0.242, p=0.047) and sclerostin (r= -0.280, p=0.024). In multiple regression analysis, periostin level was an independent variable only of CRP (β=0.160, p=0.009) and sclerostin level (β= -0.311, p=0.012).

Conclusions Serum periostin levels are low in patients with AS, and associated with disease activity, radiographic damage and sclerostin levels.

Disclosure of Interest : None declared

DOI 10.1136/annrheumdis-2014-eular.4598