Biotinidase Deficiency: Biotinidase Enzyme Analysis

Test Information

This biochemical test is a quantitative measurement of biotinidase enzyme activity and can be used as a 1st tier test for patients with a clinical suspicion of Biotinidase Deficiency. Demonstration of deficient biotinidase enzyme activity is considered the gold standard to confirm a diagnosis of Biotinidase Deficiency.

In addition, this assay can be used to clarify molecular findings in the BTD gene, to follow up abnormal newborn screening results, and to monitor patients undergoing treatment.

Turnaround Time

10 days

CPT Code(s)






Clinical Information

Biotinidase deficiency is an autosomal recessive inborn error of metabolism in which infants appear normal at birth. However, if untreated, affected infants can develop symptoms including hypotonia, ataxia, seizures, developmental delay, vision and hearing loss and cutaneous problems (eg. alopecia, dermatitis, eczema). Those diagnosed at birth should remain asymptomatic if treatment is initiated early and maintained. Biotinidase deficiency is typically detected very early because of newborn screening programs, which measure biotinidase activity in dried blood spots.


Measurement of biotinidase activity in plasma or serum is available to confirm a new diagnosis and to determine whether the patient has partial or complete biotinidase deficiency. Prenatal diagnosis and carrier testing via enzyme analysis are not available.


Biotinidase enzyme activity is determined using a p-amidobenzoic acid (PABA) colorimetric reaction that is measured by spectrophotometry at a wavelength of 546nm.

Specimen Requirements

Biotinidase activity can be assessed in either serum or plasma samples. Collect 5 ml whole blood for serum in a red top tube. Collect 5 ml of whole blood for plasma in a sodium heparin green top tube. Samples can be sent to lab as whole blood if they will arrive within 24 hours of blood draw. Alternatively, samples can be spun down and the plasma/serum pulled off and frozen before shipping. 1 ml of serum or plasma is needed for this test.

Transport Instructions

Send via courier or 24-hour delivery at room temperature. Or if plasma/serum is separate, send frozen on dry ice (preferred).

Have Questions? Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Falecia Thomas, MS, CGC

Meet Makayla Gunn

Makayla was diagnosed with Rett Syndrome in April of 2015 at the age of two. At about 18 months, we noticed she had started some repetitive hand motions, and her pediatrician was a little concerned that she did not have many words. She had learned some sign language, and was saying ‘mama’ and ‘dada’, but that was it. Then she suddenly stopped all of that. At her 2 year old check-up, the pediatrician referred us to BabyNet, SC’s early interve...

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