Kit of parts and microbiological method for assessment of the folate status in serum and red blood cells

A method for microbiological determination of folate and folic acid in a whole blood sample and assessment of the folate status of an individual, comprising the steps of:

• preparing one or more culture vessels containing a predetermined number of viable cells of Lactobacillus rhamnosus for microbiological growth and metabolism determination;
• obtaining a defined sample amount of whole blood from an individual whose folate status is to be determined;
• adding to the sample of whole blood a predetermined amount of red blood cell lysis buffer to obtain lysis of red blood cells for a release of folate species;
• adding an amount of γ-glutamyl hydrolase and/or a surfactant capable of lysosomal permeabilization to release lysosomal γ-glutamyl hydrolase from cells contained in the whole blood sample;
• treating and incubating the lysed blood sample at pH 5.5 to 7 for a sufficient time to allow enzymatic hydrolysis of the γ-glutamyl chains from folypolyglutamate species, folytetraglutamates, folypentaglutamates, and folyhexaglutamates;
• performing a microbiological assay to compare growth and metabolism in the absence or presence of varying amounts of the treated whole blood sample and/or folate calibrator to assess the individual's folate status against folate references.