Bckadbld
This test measures the activity of the branched chain keto-acid dehydrogenase (BCKDH) enzyme in your blood, which is essential for breaking down certain amino acids.
{"The BCKDH test helps diagnose Maple Syrup Urine Disease (MSUD), a rare genetic disorder","Low BCKDH activity causes harmful amino acids (leucine, isoleucine, valine) to build up in the body","Early detection through newborn screening allows for proper treatment before symptoms worsen","Treatment involves a special diet low in branched-chain amino acids","Regular monitoring helps manage the condition and prevent complications"}
Key facts at a glance
- LOINC
- 33359-1
- Short code
- BCKDC
- Synonyms
- BCKAD Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- Sodium heparin (green-top) tube or ACD tube; lithium heparin acceptable for some methodologies
- Units
- N/A
- Ref low
- 22
- Ref high
- 198
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–99 years
- Method
- Enzyme activity assay; spectrophotometric measurement of NADH/NAD+ conversion
- CPT
- 82658
- SNOMED
- 38695008
- Specimen volume
- 3-5 mL whole blood; minimum 1 mL for pediatric/neonatal samples
- Stability
- Maintain at room temperature or refrigerate (2-8°C); analyze within 24 hours of collection. Do not freeze. Ship on cold pack if transport time exceeds 4 hours.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 48–168 hours
- Order
- routine
What is this test?
The branched chain keto-acid dehydrogenase (BCKDH) test measures how well your blood contains the BCKDH enzyme. This enzyme is responsible for breaking down three essential amino acids found in protein: leucine, isoleucine, and valine. These are called branched-chain amino acids (BCAAs). The test is typically performed on a blood sample collected from a vein in your arm or from a heel stick in newborns.
Why is this test important?
This test is primarily used to diagnose and monitor Maple Syrup Urine Disease (MSUD), a rare inherited genetic disorder. In MSUD, the BCKDH enzyme is missing or not working properly, preventing the body from properly breaking down leucine, isoleucine, and valine. When these amino acids accumulate in the body, they become toxic and can cause serious health problems, including brain damage, developmental delays, and in severe cases, coma or death if left untreated.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm or, for infants, from the heel. The blood sample is then sent to a laboratory where specialists measure the activity of the BCKDH enzyme. The test may also be accompanied by measuring the levels of branched-chain amino acids in the blood to get a complete picture of how the body is processing these substances.
What do the results mean?
Normal BCKDH enzyme activity indicates that your body can properly break down branched-chain amino acids. Low or absent BCKDH activity suggests Maple Syrup Urine Disease. The results are usually given as a percentage of normal enzyme activity. Results may be interpreted as classic MSUD (very low activity, less than 2%), intermediate form (2-8% activity), or variant forms. Your doctor will explain your specific results and what they mean for your health.
What happens if the test shows MSUD?
If MSUD is diagnosed, treatment typically involves a lifelong special diet that restricts branched-chain amino acids. This includes eating specially formulated medical foods and formulas that provide nutrition without the harmful amino acids. Regular monitoring of amino acid levels is essential to adjust the diet as needed. With proper management, individuals with MSUD can lead relatively normal lives and avoid the severe complications associated with the disease.
Reference range
Adult males: 22-198 U/L; Females: 22-198 U/LN/A
No special patient preparation required. For newborn screening follow-up, sample should be collected prior to transfusion if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
Is fasting required before the BCKDH test?
How long does it take to get results?
Is the test painful?
Can MSUD be cured?
Is MSUD inherited?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy