An explanation of the decreased serum folate values found using methods that involve prior extraction of the serum.

IT had previously been reported that the newly introduced use of a chloramphenicol-resistant strain ofLactobacillus casei for microbiological assay of serum folate gives results approximately 20 per cent higher than the conventional method. It has now been shown that in these conventional techniques the prior extraction of the sera by autoclaving results in loss of the vitamin accounting for this decrease.