24) in a study comparing serum folate species measured by LC-MS/MS, microbiologic assay
, and Bio-Rad radioassay.
Erythrocyte folate extraction and quantitative determination by liquid chromatography-tandem mass spectrometry: comparison of results with microbiologic assay
The classic microbiologic assay
based on Lactobacillus casei has been automated and improved (9).
The Bio-Rad QuantaPhase II radioassay (BR), used since 1991 to monitor the folate status of the US population through the National Health and Nutrition Examination Survey (NHANES), was discontinued in 2007; 2 new methods are now employed, liquid chromatographytandem mass spectrometry (LC-MS/MS)  (3, 8, 9) and the microbiologic assay
Two assays have been discussed for future surveys: the new isotope-dilution liquid chromatography-tandem mass spectrometry method (LC-MS/MS) (2, 3) and the traditional Lactobacillus casei microbiologic assay
Clinical methods for the determination of erythrocyte folate, such as the microbiologic assay
and various immunoassays, measure only total folate (TF) and show considerable variability (5-7).
Clinical methods to determine serum folate and WBF, such as the microbiologic assay
and various immunoassays, measure only total folate (TF) and present variable results, especially for WBF (6, 7).
The microbiologic assay
using Lactobacillus casei is believed by some investigators to be a gold standard method for folate measurement.
However, it has been our experience that molecular tests are often deemed superior to traditional microbiologic assays
on the basis that they are molecular and without consideration of the performance characteristics of the various tests.
resulted in the growth of large gram-positive bacilli that were identified as C perfringens.
The rationale for (microbial) assessment and the present level of technology making such assessment feasible strongly supports the use of microbiologic assays
as adjuncts in the clinical management of periodontal disease.
Other protocols have been developed to collect excess sera, cerebrospinal fluid, or nasopharyngeal aspirates from large numbers of ED patients and compare the results of standard microbiologic assays
with those of new assays under development.