Studies with a more rapid method of vitamin B12 assay utilizing Euglena gracilis

The influence of penicillin on Lactobacillus leichmannii serum B(12) assay

The influence of penicillin on vitamin B(12) assay using L. leichmannii as the test organism was investigated, and it was found that penicillin even in a low serum concentration invalidated the test.

INVESTIGATIONS INTO THE EUGLENA METHOD FOR THE ASSAY OF THE VITAMIN B12 IN SERUM

Details are given of a modified Euglena method for the assay of B(12) in serum. Serum in very small quantities is usually inhibitory to the growth of the Euglena. In general, this inhibition is most marked when the organism is growing prolifically. For estimating serum B(12) values, a standard curve is used from B(12) standards containing 0.01 ml. of serum of low B(12) content, so that growth in test serum solutions is compared with growth in serum-containing standards. The recovery of B(12) added to serum, incomplete when estimated from aqueous standards, is now complete and the variation in results from batch to batch is markedly reduced. Various factors-such as medium, light, and inoculum-can affect growth in aqueous and serum solutions differently and are an important cause of variations between batches and laboratories. Optimal conditions were studied and they are essential for the most sensitive and accurate assay, but if the results are estimated from serum-containing standards accurate values can be obtained even under less than optimal conditions. Subnormal serum B(12) concentrations can be detected visually as early as 24 hours after the start of assay. For diagnostic purposes the assay can be read at three days, provided that appropriate dilutions are used, conditions are optimal, and growth is measured in a 1 cm. cell.

Human serum vitamin B12 assay methods--a review

The clinical importance of a reliable human serum vitamin B12 assay to aid the diagnosis of pernicious anemia (PA) cannot be overemphasized. Our review of the literature indicates that a reference method for the quantitation of serum vitamin B12 (serum B12) with the required accuracy, precision and rapidity has not been reported to-date. Controversies, debates and criticisms over human serum B12 assays (especially commercial kits) have been common-place. Various methods of quantitation of B12 reviewed in this communication include: microbiological, radioisotopic, high-performance liquid chromatography (HPLC) and the most recent radioimmunoassay (RIA) techniques. This review attempts to provide awareness of the limitations of these methods and establishes the base for eventual development of a B12 reference method in our laboratory.