Molecular DNA test to confirm a diagnosis of biotinidase (BTD) deficiency when biotinidase enzymatic activity is low. Carrier testing for individuals with a family history of BTD deficiency if familial variants are included in this test. To diagnose or rule out BTD deficiency, refer to Biotinidase, Serum (with Paired Normal Control) (0093362).
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Ataxia, hypotonia, developmental delay, respiratory problems, seizures, vision problems, hearing loss, alopecia, rash, candidiasis, metabolic ketolactic acidosis, organic aciduria and mild hyperammonemia.
Incidence: 1 in 60,000.
Inheritance: Autosomal recessive.
Cause: Deleterious mutations in the BTD gene.
Mutations Tested: c.98_104del7ins3 (G98d7i3), Q456H, R538C, and the double mutation A171T:D444H are severe; D444H alone, is mild.
Clinical Sensitivity & Specificity: 60 and 99 percent, respectively.
Methodology: Polymerase chain reaction followed by single nucleotide extension (SNE) and capillary electrophoresis.
Analytical Sensitivity & Specificity: 99 percent.
Limitations: Mutations other than those targeted in BTD will not be detected; analytic sensitivity may be compromised by rare primer site mutations. Diagnostic errors can occur due to rare sequence variations.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0051701||Biotinidase (BTD), Allele 1|
|0051702||Biotinidase (BTD), Allele 2|
|0051703||Biotinidase (BTD), Interpretation|
|2001340||BTD MUT Specimen|
- BTD mutation testing