Serum calprotectin as an inflammatory marker in psoriatic arthritis patients: Relation to disease activity and musculoskeletal ultrasound findings.

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. The use of inflammatory markers can be disappointing in PsA since they are elevated in only about half of the patients. This study aimed to measure serum calprotectin level in PsA patients and to assess its association with disease activity in PsA (DAPSA) and musculoskeletal ultrasound findings. The study included 50 PsA patients and 30 controls. All subjects underwent medical history, musculoskeletal examination, hand and wrist joints ultrasound, and laboratory assessment. The mean age of patients was 41.04±11.8 years with female: male ratio of 3:2, and the median duration of arthritis 2 years (1-4 years) and DAPSA 25 years (3-84 years). The most common finding in patients by ultrasound was synovial hypertrophy in wrist joint (32%) followed by hand joints (28%). Patients' serum calprotectin level was significantly higher (174.2 ng/ml; ranged 127.5-282.6 ng/ml) than controls 41.4 ng/ml; ranged 19.9-59.8 ng/ml) (p < 0.001). Serum calprotectin predicted the occurrence of PsA at cutoff >106.4 ng/ml (with sensitivity 98%, and specificity 86.6%; p=0.001) and predicted synovial hypertrophy in hand joints at cutoff >258.9 ng/ml (with sensitivity 71%, and specificity 83%). There was a significant relation between serum calprotectin with synovial hypertrophy (p=0.004), osteophytes (p < 0.0001), nail affection (p=0.03) and erosions (p=0.01). Serum calprotectin is a more potential predictor for PsA (p < 0.0001) compared to erythrocyte sedimentation rate (p=0.005) and C-reactive protein (p=0.001). In conclusion, serum calprotectin level is significantly high in PsA patients. It is associated with small hand joints synovitis and nail changes. This makes it a promising biomarker for defining patients with suspected PsA who do not meet specific disease criteria.