High concentrations of haptocorrin interfere with routine measurement of cobalamins in human serum and milk. A problem and its solution.
BACKGROUND
Human milk and occasional serum samples contain high concentrations of unsaturated haptocorrin, which influence accurate measurement of cobalamins.


METHODS
Cobalamins in serum samples spiked with increasing amounts of unsaturated haptocorrin were measured employing the Centaur, Cobas and Architect analysers. Cobinamide-coated EAH sepharose was employed for pretreatment of the samples. Human milk samples were collected from 24 healthy mothers. Haptocorrin was measured by ELISA.


RESULTS
The measured concentration of cobalamins either increased (Centaur analyser) or decreased (Architect, Cobas analysers) significantly for haptocorrin >10 nM, and was 220%, 52% or 45% of the expected values in a serum sample containing 50 nM haptocorrin. Following pretreatment with cobinamide-sepharose, the expected cobalamin concentration was obtained (Centaur). The milk samples contained 4.5-180 nM haptocorrin. In samples containing >10 nM haptocorrin (n=19), the median concentration of cobalamins decreased from 1.3 nM to 0.67 nM after pretreatment with cobinamide-sepharose.


CONCLUSIONS
Haptocorrin in concentrations above 10 nM influences measurement of cobalamins giving rise to falsely elevated or decreased results. Removal of unsaturated haptocorrin by pretreatment with cobinamide-sepharose solves the problem.
Lildballe
Dorte L
DL
Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark. dorla@as.aaa.dk
Hardlei
Tore F
TF
Allen
Lindsay H
LH
Nexo
Ebba
E
D053000:Analytic Sample Preparation Methods / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008895:Milk, Human / Q000737:chemistry*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014155:Transcobalamins / Q000032:analysis* / Q000302:isolation & purification*; D054928:Validation Studies as Topic; D014805:Vitamin B 12 / Q000097:blood*
D014155:Transcobalamins; D014805:Vitamin B 12