S. O’Broin

AIMS: To develop a simple microbiological assay for serum and red cell folates on 96-well microtitre plates, suitable for use in routine clinical diagnosis. METHODS: Use of a chloramphenicol resistant organism (NCIB 10463) saved time by avoiding aseptic precautions. Use of plate sealers facilitated mixing. Evaluation of assay performance included estimations of folate recovery, assay reproducibility, and response to reduced folate. Results obtained on sera (193) and red cell folates (150) were compared with those obtained using a traditional microbiological assay. RESULTS: Good recovery of folic acid added to serum and also good interassay and intra-assay precision were obtained with both serum (CV% of less than 5) and red cell folate pools (CV% of less than 5). Equimolar assay responses were obtained with folic acid, 5-formyltetrahydrofolate (L-form), and 5-methyltetrahydrofolate (L-form). The microassay correlated well with a traditional assay for estimation of folate in both serum (n = 193, r = 0.975) and red cells (n = 150, r = 0.96). CONCLUSIONS: This assay is more compact and less time consuming than the traditional assay. It is extremely economical and is easy to perform in a routine clinical laboratory.

In this simplified microbiological assay for serum vitamin B12, Lactobacillus leichmanii (NCIB 8117) adapted to tolerate high concentrations (500 mg/L) of the polymyxin antibiotic colistin sulfate is used. Results were similar in parallel experiments in which we used both the parent strain of L. leichmanii (NCIB 8117), and the new adapted strain. Evaluation of assay performance showed excellent analytical recovery of added cyanocobalamin (97%, SD 3%) and good interassay and intra-assay precision (CV less than 5%). This modified assay system obviates the need to sterilize culture medium and glassware. Consequently, assay manipulations may be carried out openly, without aseptic precautions. Moreover, this adapted organism would be suitable for use in an automated microbiological assay system.

Journal Article Influence of hematocrit on quantitative analysis of "blood spots" on filter paper Get access S O'Broin S O'Broin Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 39, Issue 6, 1 June 1993, Pages 1354–1355, https://doi.org/10.1093/clinchem/39.6.1354 Published: 01 June 1993

Dried blood spots (DBS) on filter paper have potential as a collection method in screening for haematinic deficiencies. Factors influencing the volumetric precision of uniform 'centre' punches (6.35 mm diameter) removed from dried blood spots have been evaluated. The volume of blood in each DBS punch (n = 234) was greatly influenced by both sample haematocrit (r = 0.63) and haemoglobin concentration (r = 0.63). The volume in identical punches (n = 57) also differed significantly when measured independently using either 125I human serum albumin or haemoglobin relative to the original blood sample. DBS punch volumes should be predetermined for individual batches of filter paper using the specific analyte of interest.