Serum samples are diluted and added into the microtiter plate wells coated with Lacto bacillus plantarum which metabolizes biotin. The presence of biotin both in standards [STD] and samples gives a biotin-dependent growth response. After incubation at 37°C for 48 h, the growth of Lactobacillus plantarum is measured turbidimetrically at 610 - 630 nm (alternative at 540 - 550 nm) in an ELISA-reader. A dose response curve of absorbance unit (optical density, OD at 610 nm) vs. concentration is generated using the values obtained from standard. Biotin present in the patient samples is determined directly from this curve. Sample Types: serum. Range: 0.02 - 0.18 μg/L. Sensitivity: 0.02 μg/L. Time: 48 hours ? In the late 1950s the discovery of covalently bound biotin with a coenzyme function was reported. Biotin is a growth factor present in minute amounts in every living cell. The fact that humans have a requirement for biotin has been most clearly shown in 2 situations that result in biotin deficiency: 1) prolonged consumption of raw egg whites and 2) parenteral nutrition without biotin supplementation in patients with short-gut syndrome. Biotin plays an indispensable role in numerous naturally occurring carboxylation reactions. The daily biotin requirements for adults lie between 100 and 200 mg. Renewed interest in the role of biotin in human nutrition and therapy stems from the accumulating reports of various biotin-responsive syndromes.