Serum or plasma concentration of methylthioadenosine phosphorylase (MTAP) by immunoassay
This test measures the amount of a specific enzyme in your blood, called methylthioadenosine phosphorylase (MTAP). It may be used in certain genetic or metabolic evaluations.
["MTAP levels help assess enzyme function in blood, often linked to inherited conditions."]
Key facts at a glance
- LOINC
- 81625-6
- Short code
- MTX-PG4 RBC-sCnc
- Synonyms
- MTX-PG4 RBC-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms or a family history suggestive of metabolic disorders, genetic testing for enzyme deficiencies, or if other blood tests point toward an underlying enzyme-related condition. It may also be part of a broader evaluation for conditions affecting purine metabolism.
What to Expect Before the Test
No special preparation is typically needed. You may fast for 8–12 hours before the blood draw if instructed, but always follow your provider’s specific instructions. Avoid smoking or strenuous activity for 30 minutes before the test.
What Happens During the Test
A healthcare professional will collect a blood sample from a vein in your arm using a small needle. You may feel a brief pinch, but the procedure usually takes less than 5 minutes. The blood is then sent to a lab for analysis.
What the Results Mean
Results are compared to a reference range for healthy individuals. Abnormal levels may indicate an enzyme deficiency or metabolic disorder, prompting further testing or evaluation by your provider.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
MTAP is involved in purine metabolism, and its deficiency can lead to conditions like adenosine deaminase (ADA) deficiency or other inherited metabolic disorders. Low levels may suggest a genetic predisposition to these conditions, which can affect immune function or cause developmental issues. Your provider will interpret results in the context of your symptoms and medical history.
Short name
MTAP Level
Frequently asked questions
What causes abnormal MTAP levels?
How do I prepare for this test?
Will this test hurt?
Sources
- 1
- 2Lab Tests OnlineSource
- 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