Comparative studies on the microbiological vitamin B12 assay at two laboratories

Abstract

The turbidimetric methods in routine use at 2 laboratories for the microbiological assay of vitamin B12 were compared. Attempts were made to standardize some major parts of the method, i.e., assay design, test strain (Lactobacillus leichmannii), test medium, and reference standard. The laboratories used different approaches to achieve efficient assay procedures. During a 6 yr period 4 comparative experiments were carried out. In these experiments the vitamin B12 content of 5 different products was determined in a series of independent assays at each laboratory. A satisfactory degree of agreement (difference <5%) was found for 4 of these products.