Serum homocysteine, folate and vitamin B12 levels in patients with psoriasis: a systematic review and meta-analysis

Background Patients with psoriasis are at increased risk for cardiovascular comorbidities. Previous studies examined the possible contribution of serum homocysteine, folate and vitamin B-12 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 B-12 levels in patients with psoriasis. Methods Online databases were searched on 15 February 2018 to include studies comparing serum homocysteine, folate and vitamin B-12 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 center dot 41, 95% confidence interval (CI) 0 center dot 21-0 center dot 61; I-2 = 76 center dot 7%, 18 studies], a higher prevalence of hyperhomocysteinaemia (odds ratio 3 center dot 48, 95% CI 2 center dot 08-5 center dot 83; I-2 = 41 center dot 1%, seven studies) and a lower serum folate level (SMD -0 center dot 94, 95% CI -1 center dot 49 to -0 center dot 40; I-2 = 95 center dot 6%, 14 studies). However, there was no difference in serum vitamin B-12 levels between patients with psoriasis and the control group (SMD 0 center dot 004, 95% CI -0 center dot 49 to 0 center dot 50; I-2 = 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.