Carrier screening or diagnostic testing for maple syrup urine disease type 1B for individuals of Ashkenazi Jewish descent.
Polymerase Chain Reaction/Fluorescence Monitoring
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 1 mL)
Plasma or serum. Specimens collected in sodium heparin or lithium heparin tubes.
Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month
Background Information for Maple Syrup Urine Disease, Type 1B (BCKDHB), 3 Variants:
Characteristics: Maple syrup urine disease (MSUD), type 1B most commonly presents in the first few days of life. Symptoms include irritability, poor feeding, lethargy, intermittent apnea and typically progresses to coma and death within 7 to 10 days if untreated.
Incidence: 1 in 50,000 in Ashkenazi Jewish individuals.
Inheritance: Autosomal recessive.
Cause: BCKDHB pathogenic variants.
Variants Tested: p.R183P (c.548G>C), p.G278S (c.832G>A), p.E372X (c.1114G>T).
Clinical Sensitivity: 99 percent in Ashkenazi Jewish individuals; unknown in other ethnicities.
Methodology: Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Variants other than those tested will not be detected. Diagnostic errors can occur due to rare sequence variations.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2013731||Maple Syrup Urine Disease, Specimen|
|2013732||Maple Syrup Urine Disease, Allele 1|
|2013733||Maple Syrup Urine Disease, Allele 2|
|2013734||Maple Syrup Urine Disease, Interp|