Holotranscobalamin is not influenced by decreased renal function in elderly men: the MrOS Sweden study

Abstract

Background Subclinical cobalamin deficiency is common in the elderly, but the sensitivity and specificity of serum total cobalamin for this diagnosis is poor. Serum holotranscobalamin (holoTC), a measure of biologically available cobalamin, is considered a better marker for early cobalamin depletion than total cobalamin. However, in elderly populations, health-related reference intervals for holoTC and correlations to renal function are not entirely clear. Methods HoloTC was determined with an automated microparticle enzyme immunoassay (AxSYM®) in 790 elderly non-vitamin-supplemented Swedish men, median age 75.3 years. Renal function was assessed with creatinine, cystatin C and estimated glomerular filtration rate (eGFR calculated from creatinine). Results Median holoTC was 51.8 pmol/L, the health-related reference interval 19.6–132.3 pmol/L. There was no significant difference in mean holoTC in probands with normal compared to high creatinine ( P = 0.80) and cystatin C ( P = 0.82). No significant differences between the quartiles of creatinine or cystatin C in mean of log holoTC were seen. HoloTC correlated strongly with total cobalamin ( r = 0.69, P < 0.001), weaker with eGFRcreatinine ( r = −0.09, P < 0.05) and creatinine ( r = 0.09, P < 0.05), the latter correlation was only seen in subjects with creatinine <100  µmol/L. HoloTC correlated negatively with plasma total homocysteine ( r = −0.24, P < 0.001), but not with cystatin C and age. Conclusions Serum holoTC in healthy elderly men shows the same distribution as earlier described for a younger reference population. In this group of elderly subjects, holoTC did not correlate to reduced renal function. Thus, holoTC appears to be a promising tool for evaluating cobalamin status also in elderly populations.