Plasma homocysteine, serum folic acid, serum vitamin B12, serum vitamin B6, MTHFR and risk of pseudoexfoliation glaucoma: a meta-analysis.

Background: The aim of this meta-analysis is to explore the relationship between plasma total homocysteine (tHcy) levels, serum folic acid, vitamin B12 and vitamin B6 levels, methylenetetrahydrofolate reductase (MTHFR) C677T genotype and risk of pseudoexfoliation glaucoma (PEXG).
Methods: A systematic search of EMBASE and PubMed of relevant articles was carried out for all published articles. Main outcome measures included the calculation of plasma tHcy levels, serum folic acid, vitamin B12, and vitamin B6 levels mean difference and odds ratios (OR) of MTHFR C677T genotype between cases and controls.
Results: There were 14 studies for tHcy (485 cases and 456 controls), five studies for folic acid (188 cases and 189 controls), six studies for vitamin B12 (199 cases and 225 controls), three studies for vitamin B6 (128 cases and 130 controls) and eight studies for MTHFR (479 cases and 661 controls). Overall, the mean plasma tHcy levels in cases was 3.38 umol/l (95% confidence intervals (CI): 2.35-4.42) higher than in controls. Serum folic acids, but not vitamin B12 and vitamin B6 levels, was significantly lower in cases than in controls; the weighted mean differences with 95% CI were -1.50 umol/l (-2.53, -0.46), -36.29 umol/l (-81.27, 8.68) and -0.60 umol/l (-2.55, 1.35) respectively. There was no evidence of association between the MTHFR C677T genotype and PEXG (OR = 1.28, 95% CI: 0.85, 1.93).
Conclusions: PEXG is associated with elevated plasma tHcy and low serum folic acid levels, but not serum vitamin B12, vitamin B6 levels, and MTHFR C677T genotype.