TNF and psoriatic arthritis: BMI: body mass index; PsO: psoriasis; PsA: psoriatic arthritis; SJC: swollen joint count; TJC: tender joint count; VAS: visual analogue scale; MDA: minimal disease activity; DAPSA: disease activity in psoriatic arthritis; DAS28CRP: disease activity score using 28 joint counts based on c-reactive protein; NSAID: non-steroidal anti-inflammatory drug; csDMARD: conventional synthetic disease modifying anti-rheumatic drug; TNFi: tumor necrosis factor inhibitor.