Background: Patients with psoriasis are at increased risk for cardiovascular comorbidities. Previous studies examined the possible contribution of serum homocysteine, folate and vitamin B12 to cardiovascular risks in patients with psoriasis but had conflicting conclusions. Objectives: To perform a systematic review and meta-analysis of studies on serum homocysteine, folate and vitamin B12 levels in patients with psoriasis. Methods: Online databases were searched on 15 February 2018 to include studies comparing serum homocysteine, folate and vitamin B12 levels between patients with psoriasis and controls. A random effects model was adopted to estimate odds ratios for dichotomous data and standardized mean differences (SMDs) for continuous data. Results: A comprehensive literature search identified 24 studies eligible for inclusion. Compared with controls, patients with psoriasis had a significantly higher serum homocysteine level [SMD 0·41, 95% confidence interval (CI) 0·21–0·61; I2 = 76·7%, 18 studies], a higher prevalence of hyperhomocysteinaemia (odds ratio 3·48, 95% CI 2·08–5·83; I2 = 41·1%, seven studies) and a lower serum folate level (SMD −0·94, 95% CI −1·49 to −0·40; I2 = 95·6%, 14 studies). However, there was no difference in serum vitamin B12 levels between patients with psoriasis and the control group (SMD 0·004, 95% CI −0·49 to 0·50; I2 = 92%, 11 studies). Metaregression analysis revealed a significant inverse correlation between the SMD of homocysteine levels and folate levels. Conclusions: Patients with psoriasis might have higher serum homocysteine and lower folate levels than control patients without psoriasis. However, due to significant heterogeneity and other limitations, the associations require further examinations in more studies.
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