LAUSR

Background The lack of valid biochemical markers for spondyloarthritis (SpA) patients requires searching the additional options to increase sensitivity of clinical and radiological methods in validation of changes in sacroiliac joints (SIJ). The molecular basis for the link between inflammation and new bone formation in SpA is still not clear. It has recently been shown that low serum levels of the Dickkopf-1 (Dkk-1), the natural inhibitor of Wnt protein, is associated with the formation of new syndesmophytes in patients with SpA [1]. Dkk-1 may be a main factor in blocking new bone formation [2], and might play a role of potential biomarker in SpA patients. Objectives To determine the serum levels of Dkk-1 and their relationship with active and chronic changes in SIJ on MRI, indices and laboratory parameters of disease activity and functional status in SpA patients. Methods This study includes 105 SpA patients (89.5% HLA B27 positive) and 15 healthy age- and gender- matched controls. Dkk-1 serum levels (pmol/l) were conducted by ELISA. Active inflammatory lesions in SIJ were evaluated by Spondyloarthritis Research Consortium of Canada (SPARCC) MRI SIJ score (0-72, n=69) and chronic changes by Danish scoring method (0-48). Bath Ankylosing Spondylitis Disease Activity Index (BASDAI, mm), Bath Ankylosing Spondylitis Functional Index (BASFI, mm), C-reactive protein (CRP, mg/l) and erythrocyte sedimentation rate (ESR, mm/hr) were recorded. Statistical analysis was performed using Spearman correlation coefficient, Student t-test and receiver operating characteristic (ROC) curves. Results Mean value (M±σ) of Dkk-1 was 45.1±36.3. The mean value of indices and laboratory parameters were: BASDAI – 44.5±19.3, BASFI – 31.1±23.1, CRP – 20.6±31.3, ESR – 26.8±22.0. SPARCC score was 22.2±12.0, Danish score – 19.5±9.83. Dkk-1 serum levels were lower (P < 0.01) in SpA patients compare with the controls. ROC analysis indicated that the AUC for Dkk-1 is 0.88±0.05 (p<0.001), which indicates strong capacity to differentiate groups of SpA patients with healthy controls (sensitivity - 87%, specificity - 79%). There was significant negative correlation between Dkk-1 with chronic lesions in SIJ by Danish score (r=-0.250, p=0.046). Dkk-1 showed positive correlation with CRP (r=0.216, p=0.028). There was no significant correlation of serum Dkk-1 levels with SPARCC, BASDAI, BASFI and ESR. Conclusion Dkk-1 levels are significantly lower in SpA patients compare with healthy controls and has a strong association with SpA. Dkk-1 significantly negatively correlates with chronic changes in SIJ on MRI, that may confirm that deficiency of Dkk-1 could increase progression of pathological changes in SIJ. Dkk-1 correlates only with CRP level, but none of the other indices and laboratory parameters of disease activity and functional status. References [1] Song I-H. Ann Rheum Dis. 2011; 70: 1257-1263. [2] Zhao Z. Clin Rheumatol. 2018. doi: 10.1007/s10067-018-4284-y. Disclosure of Interests Iuliia Shynkaruk: None declared, Oleg Iaremenko: None declared, Dmytro Fedkov Grant/research support from: MSD, AbbVie, ProPharma, Laboratoires Expanscience;, Consultant for: MSD, AbbVie, ProPharma, Laboratoires Expanscience;, Speakers bureau: Janssen, Kateryna Iaremenko: None declared