Measurement of 3-hydroxyisovaleric acid in urine of biotin-deficient infants and mice by HPLC

We developed an assay for measuring urinary 3-hydroxyisovaleric acid (3-HIA) using HPLC after derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH . HCl). The derivatized 3-HIA was extracted into n-hexane and separated isocratically on a C8 reversed-phase column for fatty acids (YMC-Pack FA). We used this method to measure 3-HIA in urine extracts from mice fed a biotin-deficient diet for > 4 wk and in an infant who was fed a special Japanese formula and was suspected of being biotin deficient. Urinary 3-HIA could be assayed within the range of 0.42-8.5 mmol/L with high accuracy by this method, as an indicator of biotin deficiency. Therefore, the HPLC method for 3-HIA described here may be a useful tool clinically as well as in the research laboratory.