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Test ID: BIOTS Biotinidase, Serum

Reporting Name

Biotinidase, S

Useful For

Preferred test for the diagnosis of biotinidase deficiency


Follow-up testing for certain organic acidurias

Specimen Type


Ordering Guidance

Molecular testing is available, see BTDZ / Biotinidase Deficiency, BTD Full Gene Analysis, Varies.


If measurement of biotin concentration is requested, order BIOTN / Biotin, Serum.

Specimen Required

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge immediately and aliquot serum into plastic vial.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 21 days
  Refrigerated  5 days

Reference Values

3.5-13.8 U/L

Day(s) Performed

Wednesday, Friday

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
BIOTS Biotinidase, S 1982-8


Result ID Test Result Name Result LOINC Value
50666 Specimen 31208-2
50667 Specimen ID 57723-9
50668 Source 31208-2
50669 Order Date 82785-7
50670 Reason For Referral 42349-1
50671 Method 85069-3
50672 Biotinidase, S 1982-8
50673 Interpretation 59462-2
50674 Amendment 48767-8
50675 Reviewed By 18771-6
50676 Release Date 82772-5

Clinical Information

Biotinidase deficiency is an autosomal recessive disorder caused by variants in the biotinidase gene (BTD). Age of onset and clinical phenotype vary among individuals depending on the amount of residual biotinidase activity. Profound biotinidase deficiency occurs in approximately 1 in 137,000 live births and partial biotinidase deficiency occurs in approximately 1 in 110,000 live births, resulting in a combined incidence of about 1 in 61,000. The carrier frequency for biotinidase deficiency within the general population is about 1 in 120.


Untreated profound biotinidase deficiency typically manifests within the first decade of life as seizures, ataxia, developmental delay, hypotonia, sensorineural hearing loss, vision problems, skin rash, and alopecia. Partial biotinidase deficiency is associated with a milder clinical presentation and may include cutaneous symptoms without neurologic involvement. Certain organic acidurias, such as holocarboxylase synthase deficiency, isolated carboxylase synthase deficiency, and 3-methylcrotonylglycinuria, present similarly to biotinidase deficiency. Serum biotinidase levels can help rule out these disorders.


Treatment with biotin is successful in preventing the clinical features associated with biotinidase deficiency. In symptomatic patients, treatment will reverse many of the clinical features except developmental delay, vision, and hearing complications. As a result, biotinidase deficiency is included in most newborn screening programs. This enables early identification and treatment of presymptomatic patients.


Molecular tests are useful for confirmation of diagnosis or carrier testing. When biotinidase enzyme activity is deficient, sequencing of the entire BTD gene (BTDZ / Biotinidase Deficiency, BTD Full Gene Analysis, Varies) allows for detection of disease-causing variants in affected patients. Identification of familial variants allows for testing of at-risk family members (FMTT / Familial Mutation, Targeted Testing, Varies).


While genotype-phenotype correlations are not well established, it appears that certain genetic variants are associated with profound biotinidase deficiency, while others are associated with partial deficiency.


An interpretive report is provided.


Values below 3.5 U/L are occasionally seen in specimens from unaffected patients.

Clinical Reference

1. Zempleni J, Barshop BA, Cordonier EL, et al: Disorders of biotin metabolism. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Diseases. McGraw-Hill; Accessed August 24, 2021. Available at

2. Wolf B. Biotinidase deficiency. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated June 09, 2016. Accessed August 24, 2021. Available at:

Report Available

4 to 8 days

Method Name



1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions.

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: