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.
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.
Loikas
Saila
S
Department of Clinical Chemistry, Turku University Central Hospital, Turku, Finland. sailalo@utu.fi
Koskinen
Pertti
P
Irjala
Kerttu
K
Löppönen
Minna
M
Isoaho
Raimo
R
Kivelä
Sirkka-Liisa
SL
Pelliniemi
Tarja-Terttu
TT
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*
D014155:Transcobalamins; D006710:Homocysteine; D008764:Methylmalonic Acid; D014805:Vitamin B 12