A simple binding assay for the direct determination of biotin in urine.
BACKGROUND
We have devised a simple assay to detect adequate biotin intake, which uses an alternative configuration from most existing assays.


METHODS
The assay depends on the competition of streptavidin peroxidase for immobilized biotin or soluble biotin in standards or samples. Immobilized streptavidin peroxidase is detected using tetramethylbenzidine, and the plates are read at 450 nm. The assay was normalised by determining the biotin/creatinine ratio in the urine of healthy adults. Urinary biotin excretion was measured in unsupplemented pregnant women. The half-life of biotin excretion after a single oral supplement was determined for healthy volunteers.


RESULTS
Urinary biotin excretion in unsupplemented pregnant women was 2.9+/-1.9 micromol/mol creatinine (mean+/-S.D.) and was significantly lower (p<0.001) than those of healthy males and females, which were 9.0+/-5.4 and 7.0+/-2.1 micromol/mol creatinine (mean+/-S.D.), respectively. The half-life of a single oral biotin supplement was 30-40 h, with excretion returning to basal levels at 70 h.


CONCLUSIONS
We have devised a novel binding assay for the direct determination of total biotin excretion in urine, which is suitable for routine clinical laboratory. The assay is inexpensive, simple, rapid, and could be fully automated.
Mishra
Suman
S
Steroid Laboratory, Canterbury Health Laboratories, PO Box 151, Christchurch, New Zealand.
Storer
Malina K
MK
Sherwin
Catherine M T
CM
Lewis
John G
JG
D000328:Adult; D001426:Bacterial Proteins; D001667:Binding, Competitive; D001710:Biotin / Q000008:administration & dosage / Q000652:urine*; D004800:Enzymes, Immobilized; D005260:Female; D006735:Horseradish Peroxidase; D006801:Humans; D008297:Male; D008722:Methods; D011247:Pregnancy; D013057:Spectrum Analysis
D001426:Bacterial Proteins; D004800:Enzymes, Immobilized; C058865:Strep-avidin conjugated horseradish peroxidase; D001710:Biotin; D006735:Horseradish Peroxidase