CRP and psoriasis vulgaris: The simple score, composed of CRP, IL-6 and TNF-α, with the cut-off value of 1.8, also showed satisfying predictive performance for PsA among the retrospective cohort of psoriasis vulgaris patients externally (AUC = 0.686, p = 0.010, sensitivity = 59.1%, specificity = 78.1%) (Figure 2B).