Erythrocyte mean cellular volume and its relation to serum homocysteine, vitamin B12 and folate.

Cobalamin (B12) and folate deficiency is related to both increased erythrocyte mean cellular volume (MCV) and raised serum total homocysteine (tHcy) values. Furthermore, there are indications that B12 and folate serum values do not represent the tissue status of the two vitamins exactly. Therefore, a direct relationship between MCV and tHcy, if demonstrated, could support the hypothesis that tHcy is a better indicator for the cited vitamin status than the serum levels of B12 and folate. We studied MCV, gamma glutamyl transferase (GGT), serum B12, folate and tHcy values in 200 hospitalized patients. There was a significant correlation of MCV with GGT (r = 0.266, P < 0.001) and with tHcy (r = 0.248, P < 0.001), but not with serum B12 and folate. Stepwise multiple linear regression with MCV as dependent and GGT, B12, folate and tHcy as independent variables, respectively, revealed significant associations of MCV with GGT (B = 2.18, 95% CI 0.95-3.42, P = 0.001) and tHcy (B = 3.33, 95% CI 1.26-5.39, P = 0.002). By removing tHcy from this model, serum B12 became a significant predictor of MCV (B = -1.70, 95% CI -3.25 to -0.15, P = 0.032). Serum folate was not significantly associated with MCV in multivariate analysis. In conclusion, the present study confirms indications that serum B12 and folate values lack clinical sensitivity and specificity in diagnosing vitamin deficiency states by showing MCV was better associated to tHcy, than to B12 or folate serum levels. This observation demonstrates that tHcy may be useful in diagnosing patients with B12 and/or folate deficiency.