Determination of erythrocyte vitamin B12 activity.

Data presented in this paper show that there is no significant difference between plasma and serum vitamin B₁₂ activity when EDTA is used as the anticoagulant. By drawing 5 ml of blood into a tube containing EDTA, the whole blood and plasma B₁₂ activity can be measured using Lactobacillus leichmannii for the assay as the test organism. Erythrocyte B₁₂ levels can be obtained by difference after correcting for hematocrit. Sodium heparin appears to inhibit the growth of L. leichmannii. [ABSTRACT FROM AUTHOR]