Chitinase-3-like protein 1 (YKL-40) is a biomarker of severity of joint involvement in psoriatic arthritis

Introduction
Psoriasis is an inflammatory disease of a complex pathogenesis and arthritis is one of its most common complications. The biological role of chitinase-3-like protein 1 remains unknown. It is suggested that this protein takes part in processes such as proliferation, inflammation and tissue remodelling.

Aim
To determine whether YKL-40 can be a useful biomarker in psoriatic arthritis.

Material and Methods
The study was performed on 42 patients with psoriatic arthritis: 28 men and 14 women, aged from 24 to 71 years. All patients met the diagnostic criteria (CASPAR) for psoriatic arthritis. The severity of psoriatic arthritis was assessed using 28-joint Disease Activity Score with CRP. The assessment of skin lesions was performed by Psoriasis Area and Severity Index (PASI) and, additionally, the Body Surface Area (BSA) was calculated. Blood samples were taken to measure the serum concentration of YKL-40, as well as C-reactive protein, erythrocyte sedimentation rate, white blood cell count and neutrophil count.

Results
YKL-40 serum levels were significantly higher in patients with psoriatic arthritis, compared to the control group. Moreover, a significant positive correlation between the activity of psoriatic arthritis measured by DAS 28 and serum level of YKL-40 was found. There was a positive correlation between serum YKL-40 and BSA, as well as a distinct trend towards significance between YKL-40 and PASI score.

Conclusions
YKL-40 can be a useful biomarker for both diagnosing and monitoring joint involvement in psoriatic patients.