RT Journal Article SR Electronic T1 Extraction of serum vitamin B12 for radio-isotopic and Lactobacillus leichmannii assay. JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 531 OP 539 DO 10.1136/jcp.28.7.531 VO 28 IS 7 A1 Raven, J L A1 Robson, M B YR 1975 UL http://jcp.bmj.com/content/28/7/531.abstract AB The protein precipitates discarded during the extraction process of the Lactobacillus leichmannii vitamin B12 assay have been shown to contain significant amounts of vitamin B12. This loss of vitamin B12 provide a satisfactory explanation for many of the descrepancies between the serum vitamin B12 values obtained by the L. leichmannii method and the radio-isotopic method of Raven et al (1969). It is possible to produce lower results by the method of Raven et al (1969)by incorporating into that method the L. leichmannii extraction process; it is also possible to produce higher results by the L. leichmannii method using a papain extraction process.