Renal impairment compromises the use of total homocysteine and methylmalonic acid but not total vitamin B12 and holotranscobalamin in screening for vitamin B12 deficiency in the aged

Abstract

Vitamin B(12) deficiency and renal impairment are common in the aged, and therefore the screening test for vitamin B(12) deficiency should not be affected by renal function. Renal impairment has been associated with increased concentrations of plasma total homocysteine and methylmalonic acid, as well as increased total vitamin B(12) and holotranscobalamin concentrations. The effect of renal impairment on vitamin B(12)-related biochemical variables was assessed in 1011 aged subjects. Renal function as indicated by serum cystatin C correlated strongly with plasma total homocysteine (r(s)=0.53, p<0.001) and serum methylmalonic acid (r(s)=0.27, p<0.001), but not with serum total vitamin B(12) (r(s)=-0.04, p=0.227) or holotranscobalamin (r(s)=-0.01, p=0.817). Either total vitamin B(12) or holotranscobalamin rather than homocysteine or methylmalonic acid should be used when screening an aged population prone to renal impairment.