An indirect enzyme-linked assay was developed for quantifying biotin concentrations in human sera. Biotin standard solutions or unknown samples are preincubated with streptavidin-conjugated horseradish peroxidase (streptavidin-HRP) and added to plates coated with biotinylated bovine IgG (B-IgGb). The concentration of the streptavidin-HRP is such that the streptavidin binding sites are sufficient to bind apparently all the biotin present in samples, whereas, the remaining sites are inversely proportional to the amount of biotin in analysed sample. These sites could subsequently interact with the immobilized B-IgGbproviding signal. The assay demonstrated dynamic range 5 to 640 ng/L, detection limit 2 ng/L, intra- and interassay C.V., 1.6–3.9 % and 3.7–7.2 % respectively, recovery 100–114% and linear recovery 90–117%. Serum biotin determined: healthy individuals 66 to 600 ng/L, pregnant women (≥ 36weeks) 60 to 360 ng/L, and patients under chronic haemodialysis 0.56 to 1.62 μg/L. The method described is among those few which have been experimentally evaluated for their capabilitity of assessing biotin in human sera.
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