Can pretreatment serum calcium level predict the efficacy of methotrexate in the treatment of severe plaque psoriasis?

Background: The efficacy of methotrexate (MTX) varies in the treatment of psoriasis. Objective: We sought to identify an indicator from routine pretreatment tests to predict MTX efficacy in the treatment of psoriasis. Methods: In a retrospective analysis of 77 psoriatic patients, the correlation between MTX efficacy and pretreatment routine test results was analyzed with Spearman correlation. The potential risks were further evaluated with a linear regression model. Receiver operating characteristic analysis was performed to examine the effectiveness of serum total calcium (tCa) to predict the effect of MTX on psoriasis. The highest Youden index was used to determine the cutoff point, with which the positive and negative predictive values were calculated. Synergistic effects of MTX and calcium on keratinocyte growth and psoriasis-like mouse model were also investigated. Results: The pretreatment tCa level exhibited the closest association with MTX efficacy. The relative psoriasis improvement with tCa was 61.07% (95% confidence interval, 42.85-79.29; P < .001) and better improvements were observed in patients with higher tCa (r = 0.588; P < .002). MTX inhibited keratinocyte growth, which was enhanced synergistically by calcium. In a psoriasis-like mouse model, MTX strongly inhibited epidermis proliferation in the high-calcium group. Limitations: One limitation of our study is the relatively small sample size. Conclusion: Pretreatment tCa level has the highest correlation with MTX efficacy, which might be useful in predicting beneficial treatment results in psoriasis. Larger studies are required to confirm our findings.