Torch Panel Avidity IgG Test
Short Name: TORCH Avidity IgG
Also known as: TORCH Panel IgG Avidity Test, TORCH Avidity Panel, IgG Avidity for TORCH Infections
Torch Panel Avidity IgG Test test available at DNA Labs India for ₹1,603. Uses Enzyme Immunoassay (ELISA) on Serum samples. Results in Samples accepted by 9 am on Monday, Wednesday, or Friday are reported on the same day. If samples arrive later, results are delivered the next working day.. Free home collection in 300+ cities across India.
🩺 Medically Reviewed By
Dr Kothari Ramesh Shantilal
Consultant Microbiologist · Reg: 27670
Last reviewed: September 7, 2026
Overview
The purpose of the TORCH Panel Avidity IgG Test is to determine the phase of a TORCH infection by measuring the avidity (functional affinity) of IgG antibodies. Low avidity indices (typically less than 30%) indicate a current or recent primary infection, which is clinically important in pregnant women because primary infection during pregnancy can cause severe congenital infections in the fetus. High avidity (greater than 60%) confirms past infection, thus reassuring low fetal risk. This discrimination is essential for clinical decisions regarding diagnostic amniocentesis, fetal ultrasound monitoring, and consideration of antiviral or immune-modulatory therapy. The test also helps differentiate between primary infection and reinfection/reactivation, which may have different clinical implications.
- Test Code
- 3696
- CPT Code
- 86644
- ICD Code
- Z11.59
- Price
- ₹1,603
- Sample Type
- Serum
- Result Time
- Samples accepted by 9 am on Monday, Wednesday, or Friday are reported on the same day. If samples arrive later, results are delivered the next working day.
- Fasting Required
- No
- Method
- Enzyme Immunoassay (ELISA)
Sample Collection
No special preparation is required. The patient may continue normal diet and hydration. Inform the laboratory about any current medications or supplements.
Method: Venipuncture
Laboratory Analysis
Blood will be collected from a vein in the arm using standard aseptic techniques. The procedure takes about 2-3 minutes and is well tolerated.
Report Delivery
After collection, pressure is applied to the puncture site to prevent bruising. The patient can resume normal activities immediately. Reports are delivered digitally via WhatsApp, email, or online portal.
Timeline: Samples accepted by 9 am on Monday, Wednesday, or Friday are reported on the same day. If samples arrive later, results are delivered the next working day.
Patient Instructions
About This Test
Who Should Get This Test
The purpose of the TORCH Panel Avidity IgG Test is to determine the phase of a TORCH infection by measuring the avidity (functional affinity) of IgG antibodies. Low avidity indices (typically less than 30%) indicate a current or recent primary infection, which is clinically important in pregnant women because primary infection during pregnancy can cause severe congenital infections in the fetus. High avidity (greater than 60%) confirms past infection, thus reassuring low fetal risk. This discrimination is essential for clinical decisions regarding diagnostic amniocentesis, fetal ultrasound monitoring, and consideration of antiviral or immune-modulatory therapy. The test also helps differentiate between primary infection and reinfection/reactivation, which may have different clinical implications.
How to Prepare
- Sample type: Serum from SST
- Volume: 3 mL (1.5 mL minimum)
- Transport: Refrigerated or frozen
- Ship refrigerated or frozen
- No fasting required
Doctor's Notes
Reviewed by Dr Kothari Ramesh Shantilal — MBBS, MD (Microbiology) · Reg. No. 27670
"IgG avidity testing is a crucial step in differentiating primary from past infections during pregnancy. It helps clinicians decide on further monitoring and management to prevent congenital transmission."
Last medically reviewed: September 7, 2026
Test Parameters & Specifications
Sample Stability
- Hemolyzed or lipemic specimens
- Improperly labeled samples
- Clotted or insufficient sample volume
- Samples stored beyond stability limits
Understanding Your Results
IgG Avidity Index < 30% (Low)
Recent primary infection (likely within the last 3-4 months). Increased risk of fetal transmission if acquired during pregnancy. Further evaluation and management by a specialist recommended.
IgG Avidity Index 30-40% (Borderline/Equivocal)
Indeterminate. Repeat testing after 2-4 weeks or perform additional assays such as IgM and IgG quantification to clarify infection timing.
IgG Avidity Index > 40% (High)
Past infection (more than 4-6 months prior). Low risk of congenital transmission. Reassuring for the current pregnancy, though standard obstetric care should continue.
If you are pregnant and experience symptoms like fever, rash, or lymphadenopathy, or if you have been exposed to a known TORCH infection, consult your obstetrician immediately. An early TORCH panel avidity test can guide management. Also, if you receive an abnormal or high-risk result, meet with an infectious disease specialist or maternal-fetal medicine expert for further guidance.
Limitations
- ⚠Avidity index cutoff values vary between laboratories and assay kits; results should be interpreted with local reference ranges
- ⚠A single avidity result cannot always replace paired IgG/IgM serology and clinical assessment
- ⚠Low avidity does not always confirm recent infection in immunocompromised patients
- ⚠The test may not discriminate between primary and recurrent infection in certain cases such as HSV
- ⚠Not all TORCH infections have validated avidity assays; clinical correlation is essential
Risks & Considerations
- ●Minimal discomfort or bruising at the needle site
- ●Small risk of hematoma
- ●Dizziness or fainting (rare)
- ●Infection at the puncture site (extremely rare with proper aseptic technique)
Interfering Factors
- ●Immunocompromised states (e.g., HIV, transplant) may alter IgG avidity maturation
- ●Recent blood transfusion or administration of intravenous immunoglobulin can affect results
- ●Autoimmune diseases with polyclonal hypergammaglobulinemia may interfere with binding
- ●Hemolyzed or lipemic samples may affect assay accuracy
- ●Antibiotic or antiviral therapy may delay avidity maturation
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Frequently Asked Questions
What is the TORCH Panel Avidity IgG Test?
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