TPMT (Thiopurine Methyl Transferase) Genotyping Test
Short Name: TPMT Genotyping Test
Also known as: Thiopurine Methyltransferase Genotyping, TPMT Gene Test, TPMT Pharmacogenomic Test, TPMT Enzyme Genotyping, Thiopurine S-Methyltransferase Genotyping
TPMT (Thiopurine Methyl Transferase) Genotyping Test test available at DNA Labs India for ₹7,200. Uses Real Time PCR on Whole Blood samples. Results in Sample accepted on Monday and Thursday by 11:00 AM. Reports available on Wednesday and Saturday.. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr SHAILAJA RAGHUNATH MURDESHWAR
Consultant Physician · Reg: 8052
Last reviewed: September 7, 2026
Overview
The purpose of the TPMT Genotyping Test is to identify genetic variants in the TPMT gene that affect enzyme activity, enabling personalized dosing of thiopurine medications. Measurement of TPMT activity is encouraged prior to commencing treatment with thiopurine drugs such as Azathioprine, 6-Mercaptopurine, and 6-Thioguanine. Patients with low or absent TPMT activity are at a heightened risk of drug-induced bone marrow toxicity due to the accumulation of unmetabolized drug. This test helps clinicians make informed prescribing decisions to prevent serious adverse drug reactions.
- Test Code
- 1445
- Price
- ₹7,200
- Sample Type
- Whole Blood
- Result Time
- Sample accepted on Monday and Thursday by 11:00 AM. Reports available on Wednesday and Saturday.
- Fasting Required
- No
- Method
- Real Time PCR
Sample Collection
No fasting or special preparation is required. A duly filled Genomics Clinical Information Requisition Form (Form 20) is mandatory before sample collection. Inform the phlebotomist about any recent blood transfusions or current medications.
Method: Venipuncture
Laboratory Analysis
A venipuncture will be performed to collect 4 mL (minimum 2 mL) of whole blood into a Lavender Top (EDTA) tube. The procedure typically takes less than 5 minutes.
Report Delivery
Apply gentle pressure to the puncture site with a cotton ball. The sample will be shipped refrigerated to the laboratory. Do not freeze the sample. Avoid strenuous activity with the collection arm for a few hours.
Timeline: Sample accepted on Monday and Thursday by 11:00 AM. Reports available on Wednesday and Saturday.
Patient Instructions
About This Test
Who Should Get This Test
The purpose of the TPMT Genotyping Test is to identify genetic variants in the TPMT gene that affect enzyme activity, enabling personalized dosing of thiopurine medications. Measurement of TPMT activity is encouraged prior to commencing treatment with thiopurine drugs such as Azathioprine, 6-Mercaptopurine, and 6-Thioguanine. Patients with low or absent TPMT activity are at a heightened risk of drug-induced bone marrow toxicity due to the accumulation of unmetabolized drug. This test helps clinicians make informed prescribing decisions to prevent serious adverse drug reactions.
How to Prepare
- Duly filled Genomics Clinical Information Requisition Form (Form 20) is mandatory
- Collect 4 mL (2 mL min.) whole blood in 1 Lavender Top (EDTA) tube
- Ship refrigerated. DO NOT FREEZE
- Label the sample clearly with patient name, date of birth, and collection date
- Avoid sample collection within 4 weeks of a blood transfusion
Doctor's Notes
Reviewed by Dr SHAILAJA RAGHUNATH MURDESHWAR — MBBS, MD (General Medicine) · Reg. No. 8052
"TPMT genotyping is an essential pre-treatment investigation before initiating thiopurine therapy. Patients identified as intermediate or poor metabolizers require dose reduction or alternative therapy to avoid life-threatening myelosuppression. I recommend this test for every patient before prescribing Azathioprine, 6-Mercaptopurine, or 6-Thioguanine."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Sample received frozen
- Sample collected in incorrect tube (non-EDTA)
- Insufficient sample volume (less than 2 mL)
- Hemolyzed or clotted sample
- Missing or incomplete Genomics Clinical Information Requisition Form (Form 20)
- Unlabeled or mislabeled sample
Understanding Your Results
Wild Type / Normal Homozygous (TPMT*1/*1)
Low risk of thiopurine-induced myelosuppression
Heterozygous (One variant allele, e.g., TPMT*1/*3A, TPMT*1/*3C)
Moderate risk of thiopurine-induced myelosuppression; dose adjustment recommended
Homozygous Variant (Two variant alleles, e.g., TPMT*3A/*3A)
High risk of severe, life-threatening myelosuppression; alternative therapy or major dose reduction required
Consult your doctor immediately if you experience nausea, vomiting, diarrhea, fever, jaundice, unexplained bruising or bleeding, or unusual fatigue while taking thiopurine drugs. These symptoms may indicate drug toxicity related to TPMT deficiency. Always share your TPMT genotyping results with your treating physician before starting or adjusting thiopurine therapy.
Limitations
- ⚠This test identifies only the most common TPMT variants and may not detect all rare mutations
- ⚠Genotyping predicts enzyme activity but does not directly measure it
- ⚠Results should be interpreted in conjunction with clinical history and other laboratory findings
- ⚠This test does not replace therapeutic drug monitoring during thiopurine therapy
- ⚠Ethnic-specific rare variants may not be covered by this panel
Risks & Considerations
- ●Minor bruising or discomfort at the blood collection site
- ●Rare risk of infection at the puncture site
- ●Slight risk of lightheadedness during blood draw
Interfering Factors
- ●Recent blood transfusions may affect genotyping accuracy
- ●Concurrent use of certain medications may interfere with sample quality
- ●Improper sample storage or handling may compromise results
- ●Sample hemolysis may affect DNA extraction quality
Compare With Similar Tests
| Test | TPMT (Thiopurine Methyl Transferase) Genotyping Test | TPMT Enzyme Activity Assay | NUDT15 Genotyping | 6-Thioguanine Nucleotide Monitoring |
|---|---|---|---|---|
| Comparison | TPMT (Thiopurine Methyl Transferase) Genotyping Test |
Frequently Asked Questions
What is the TPMT Genotyping Test?
Why is TPMT testing important before starting thiopurine drugs?
What sample is required for the TPMT Genotyping Test?
Is fasting required for the TPMT Genotyping Test?
How long does it take to get the TPMT Genotyping Test results?
What are the common TPMT gene variants tested?
What happens if my TPMT test shows low or absent enzyme activity?
Who should get a TPMT Genotyping Test?
What is the cost of the TPMT Genotyping Test in India?
Is home sample collection available for the TPMT Genotyping Test?
Can TPMT Genotyping results change over time?
What is the difference between TPMT genotyping and TPMT enzyme activity testing?
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