Objective: To study the nail abnormalities quality of life and serum inflammatory marker in psoriasis patients in relation to psoriatic arthritis.

Material and Method: A case-control study was performed at Phramongkutklao Hospital between January 1 and October 31, 2013. The demographic data and laboratory investigations of 55 cases of psoriasis patients with and without arthritis were compared.

Results: Psoriasis patients with arthritis had more nail abnormalities than those without (43 vs. 29, p-value = 0.005). The most common type of nail involvement was onycholysis. Quality of life in psoriasis patients with arthritis was worse than those without (visual analog score 50.24±23.13 vs.20.77±17.33, p-value <0.001). Nail involvement, ESR 37 mm/hour or more and hs-CRP 2.94 mg/dL or more were associated with arthritis in psoriasis (sensitivity 74.55%, specificity 58.18%, and area under curve 0.7286, and sensitivity 69.09%, specificity 60.00%, and area under curve 0.682 for ESR and hs-CRP respectively).

Conclusion: Psoriatic arthritis has more nail abnormalities. Arthritis is associated with worse quality of life in psoriasis. Nail abnormalities, ESR 37 mm/hour or more and hs-CRP 2.94 mg/dL or greater may predict arthritis in psoriasis patients.

Keywords: Psoriasis, Arthritis, Nail abnormalities, ESR, hs-CRP