This test is used to diagnose biotinidase deficiency in clinically symptomatic patients and to confirm the diagnosis suspected from abnormal newborn screening.Biotinidase deficiency is an autosomal recessive disorder characterized by central nervous system and skin manifestations. Individuals with profound deficiency usually present around 3 months of age, but may present as early as the first week of life and as late as 10 years of age. If untreated, the patient may experience seizures, developmental delay, skin lesions, and irreversible sensorineural deafness.