TPMT Gene TPMT deficiency NGS Genetic Test
Short Name: TPMT NGS Genetic Test
Also known as: TPMT Genotyping Test, Thiopurine S-Methyltransferase Gene Test, TPMT Pharmacogenomic Test, TPMT Mutation Analysis, Thiopurine Drug Sensitivity Test
TPMT Gene TPMT deficiency NGS Genetic Test test available at DNA Labs India for ₹20,000. Uses Next-Generation Sequencing (NGS), Targeted Gene Panel Sequencing, Bioinformatic Variant Analysis on Blood or Extracted DNA or One Drop Blood on FTA Card samples. Results in 3 to 4 Weeks from sample receipt at the laboratory. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr SULOCHANA HEMCHANDRA HOLLA
Consultant Medical Geneticist · Reg: 8532
Last reviewed: September 7, 2026
Overview
The purpose of the TPMT Gene Deficiency NGS Genetic Test is to identify genetic variants in the TPMT gene that affect enzyme activity and thiopurine drug metabolism. This test enables clinicians to stratify patients into normal (homozygous wild-type), intermediate (heterozygous), or poor (homozygous or compound heterozygous variant) metabolizer categories before initiating thiopurine therapy. By identifying at-risk patients, the test guides appropriate dose adjustments or selection of alternative therapies, thereby preventing severe adverse drug reactions including myelosuppression, hepatotoxicity, gastrointestinal toxicity, and increased infection risk. This pharmacogenomic test is recommended by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and recognized by the FDA as a companion diagnostic for thiopurine medications.
- Test Code
- 2272
- CPT Code
- 81401
- ICD Code
- Z13.0
- Price
- ₹20,000
- Sample Type
- Blood or Extracted DNA or One Drop Blood on FTA Card
- Result Time
- 3 to 4 Weeks from sample receipt at the laboratory
- Fasting Required
- No
- Method
- Next-Generation Sequencing (NGS), Targeted Gene Panel Sequencing, Bioinformatic Variant Analysis
Sample Collection
No special preparation is required. Patients do not need to fast before sample collection. Inform the healthcare provider about any recent blood transfusions within the past 12 weeks, current medications, and relevant clinical and family history. A genetic counseling session is recommended prior to testing to prepare a pedigree chart and discuss the implications of potential results.
Method: Venipuncture
Laboratory Analysis
A trained phlebotomist will collect approximately 3-5 mL of venous blood into an EDTA (lavender top) vacutainer tube. Alternatively, one drop of blood can be spotted on an FTA card. The procedure takes approximately 5-10 minutes and involves minimal discomfort similar to a routine blood draw.
Report Delivery
Apply gentle pressure to the puncture site with cotton or a bandage for 3-5 minutes. Mild bruising may occur at the site and typically resolves within a few days. Results are delivered within 3-4 weeks via online portal, email, or WhatsApp. A follow-up genetic counseling session is recommended to discuss results and clinical implications.
Timeline: 3 to 4 Weeks from sample receipt at the laboratory
Patient Instructions
About This Test
Who Should Get This Test
The purpose of the TPMT Gene Deficiency NGS Genetic Test is to identify genetic variants in the TPMT gene that affect enzyme activity and thiopurine drug metabolism. This test enables clinicians to stratify patients into normal (homozygous wild-type), intermediate (heterozygous), or poor (homozygous or compound heterozygous variant) metabolizer categories before initiating thiopurine therapy. By identifying at-risk patients, the test guides appropriate dose adjustments or selection of alternative therapies, thereby preventing severe adverse drug reactions including myelosuppression, hepatotoxicity, gastrointestinal toxicity, and increased infection risk. This pharmacogenomic test is recommended by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and recognized by the FDA as a companion diagnostic for thiopurine medications.
How to Prepare
- Use an EDTA (Lavender Top) vacutainer for whole blood collection or an FTA card for a single blood drop
- Ensure proper labeling of the sample with patient name, date of birth, sample ID, and date of collection
- Avoid hemolysis during blood draw by using appropriate needle gauge and gentle handling
- Do not freeze whole blood samples; store at 2-8°C if not shipped immediately
- Ship samples at ambient room temperature in appropriate biohazard packaging within 48 hours of collection
- Inform the laboratory if the patient has received a blood transfusion in the past 12 weeks
- Include a completed test requisition form with clinical history and family pedigree information
Doctor's Notes
Reviewed by Dr SULOCHANA HEMCHANDRA HOLLA — MBBS, MD (Medical Genetics) · Reg. No. 8532
"TPMT genotyping is an essential pharmacogenomic test before initiating thiopurine therapy. Identifying patients with intermediate or poor metabolizer status helps prevent life-threatening myelosuppression and hepatotoxicity. In my oncology practice, I recommend TPMT testing for every patient prior to starting azathioprine, 6-mercaptopurine, or thioguanine, particularly those undergoing maintenance chemotherapy for acute lymphoblastic leukemia where sustained thiopurine exposure significantly increases toxicity risk in TPMT-deficient individuals."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Hemolyzed or clotted blood samples
- Samples collected in incorrect (non-EDTA) anticoagulant tubes
- Insufficient sample volume (less than 2 mL)
- Samples without proper labeling or identification
- Samples older than 7 days at room temperature without prior refrigeration
- Leaking or damaged sample containers
Understanding Your Results
Normal Metabolizer (Wild-type: *1/*1)
TPMT enzyme activity is within normal range. These patients can generally receive standard starting doses of thiopurine drugs. Routine monitoring of CBC and liver function tests is still recommended per standard clinical protocols.
Clinical action: Standard thiopurine dosing per approved prescribing information.
Intermediate Metabolizer (Heterozygous: *1/*2, *1/*3A, *1/*3B, *1/*3C, etc.)
TPMT enzyme activity is reduced (typically 50-70% of normal). These patients have a moderately increased risk of myelosuppression with standard thiopurine doses. Dose reduction is recommended.
Clinical action: Reduce thiopurine dose by approximately 30-50% (or consider alternative therapy). Increase frequency of CBC monitoring, especially during the initial weeks of treatment.
Poor Metabolizer (Homozygous or Compound Heterozygous: *2/*2, *3A/*3A, *3C/*3C, *2/*3A, etc.)
TPMT enzyme activity is absent or very low (typically <10% of normal). These patients are at extremely high risk for severe, life-threatening myelosuppression with standard thiopurine doses.
Clinical action: Avoid thiopurine drugs entirely if possible. If thiopurines are clinically essential, significantly reduce the dose (by 90% or more) and implement intensive hematologic monitoring. Consider alternative immunosuppressive or chemotherapeutic agents.
Variants of Uncertain Significance (VUS) Detected
Rare or novel TPMT variants were identified that have insufficient evidence to classify as pathogenic or benign. The clinical impact on TPMT enzyme activity is not well established.
Clinical action: Consult with a clinical geneticist. Consider TPMT phenotyping (enzyme activity assay) as a complementary test. Apply standard caution with thiopurine dosing and close monitoring.
Consult your doctor or genetic counselor if your test reveals intermediate or poor metabolizer status, if you are about to start or are currently receiving thiopurine therapy, if you have experienced unexplained blood count abnormalities while on thiopurine medications, if a variant of uncertain significance (VUS) is detected, or if you have questions about the implications of your genetic results for treatment planning or family members.
Limitations
- ⚠This test detects known and common pathogenic variants in the TPMT gene; rare or novel variants of uncertain significance (VUS) may be identified
- ⚠Genotyping does not account for epigenetic factors, gene-gene interactions, or environmental influences on enzyme activity
- ⚠Phenotype may not always correlate perfectly with genotype due to regulatory region variants or post-transcriptional modifications not covered by this test
- ⚠This test does not evaluate the NUDT15 gene, which is also important for thiopurine metabolism and toxicity risk, particularly in South Asian populations
- ⚠Results should always be interpreted in conjunction with clinical history and by a qualified healthcare professional
- ⚠Somatic mutations in tumor tissue may differ from germline genotype
Risks & Considerations
- ●Minimal risk associated with blood collection: slight pain or bruising at the needle insertion site
- ●Rare possibility of vasovagal reaction (feeling faint) during or after blood draw
- ●Very small risk of infection at the puncture site
- ●Psychological impact of learning about genetic predisposition to drug sensitivity (addressed through genetic counseling)
Interfering Factors
- ●Recent blood transfusions may dilute patient DNA with donor DNA, potentially affecting genotyping accuracy
- ●Hematologic malignancies with high blast counts may yield DNA that does not represent the patient's germline genotype
- ●Hemolyzed or degraded blood samples may compromise DNA quality and sequencing results
- ●Concurrent use of certain medications does not directly affect genotyping but may influence phenotypic expression
Compare With Similar Tests
| Test | TPMT Gene TPMT deficiency NGS Genetic Test | PCR-Based TPMT Genotyping | Sanger DNA Sequencing | TPMT Phenotyping (Enzyme Activity Assay) |
|---|---|---|---|---|
| Comparison | TPMT Gene TPMT deficiency NGS Genetic Test |
Frequently Asked Questions
What is the TPMT gene and why is it important?
Who should get the TPMT Gene Deficiency NGS Genetic Test?
What is the cost of the TPMT Gene Deficiency NGS Genetic Test in India?
How is the TPMT genetic test performed?
What does it mean to be a poor metabolizer for TPMT?
What is the difference between TPMT genotyping and TPMT phenotyping?
How long does it take to get the TPMT genetic test results?
What files and reports do I receive with the TPMT genetic test?
Is the TPMT genetic test a one-time test or does it need to be repeated?
Does the TPMT genetic test cover all possible variants in the gene?
Is home sample collection available for the TPMT genetic test?
What should I do if my TPMT test shows a variant of uncertain significance (VUS)?
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