title: 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.
authors.affiliation: Section of Hematology and Coagulation, Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Catharina
authors.initials: C
authors.lastname: Lewerin
authors.forename: Herman
authors.initials: H
authors.lastname: Nilsson-Ehle
authors.forename: Stefan
authors.initials: S
authors.lastname: Jacobsson
authors.forename: Magnus K
authors.initials: MK
authors.lastname: Karlsson
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlsson
authors.forename: Dan
authors.initials: D
authors.lastname: Mellström
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis / Q000592:standards*; D005919:Glomerular Filtration Rate; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007668:Kidney / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D012016:Reference Values; D013548:Sweden; D014155:Transcobalamins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D014155:Transcobalamins; D006710:Homocysteine
keywords: Creatinine; analytes; clinical studies; evaluation of new methods; laboratory methods; nutrition