MTHFR and triple-A syndrome: In our subgroup meta-analysis of 6 studies[13,15,21–23,25] of AAA with a diameter ≥55 mm, a significant association between the MTHFR C677T polymorphism and AAA risk was observed (TT + CT vs CC: OR = 1.55, 95% CI = 1.07–2.24, P = 0.02).