title: 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: BACKGROUND
  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.
  
  
  METHODS
  The effect of renal impairment on vitamin B(12)-related biochemical variables was assessed in 1011 aged subjects.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Clinical Chemistry, Turku University Central Hospital, Turku, Finland. sailalo@utu.fi
authors.forename: Saila
authors.initials: S
authors.lastname: Loikas
authors.forename: Pertti
authors.initials: P
authors.lastname: Koskinen
authors.forename: Kerttu
authors.initials: K
authors.lastname: Irjala
authors.forename: Minna
authors.initials: M
authors.lastname: Löppönen
authors.forename: Raimo
authors.initials: R
authors.lastname: Isoaho
authors.forename: Sirkka-Liisa
authors.initials: SL
authors.lastname: Kivelä
authors.forename: Tarja-Terttu
authors.initials: TT
authors.lastname: Pelliniemi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007674:Kidney Diseases / Q000097:blood*; D008722:Methods; D008764:Methylmalonic Acid / Q000097:blood*; D014155:Transcobalamins / Q000032:analysis*; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000175:diagnosis*
chemical_list: D014155:Transcobalamins; D006710:Homocysteine; D008764:Methylmalonic Acid; D014805:Vitamin B 12