Immunoglobulin IgG Subclass 4 Test
Short Name: IgG4 Subclass Test
Also known as: IgG4 Subclass Test, IgG Subclass 4 Blood Test, IgG4 Antibody Test, Immunoglobulin G Subclass 4 Test, Serum IgG4 Level Test
Immunoglobulin IgG Subclass 4 Test test available at DNA Labs India for ₹9,000. Uses Nephelometry on Serum samples. Results in Same-day reports are available for samples received Monday or Thursday by 4:00 PM at the laboratory.. Free home collection in 300+ cities across India.
Overview
The purpose of the Immunoglobulin IgG Subclass 4 Test is to measure the concentration of IgG4 antibodies in the blood. This test serves two primary clinical purposes: (1) to diagnose IgG4-related disease (IgG4-RD), a chronic inflammatory condition characterized by elevated serum IgG4 levels and tissue infiltration by IgG4-positive plasma cells, and (2) to identify selective IgG4 subclass deficiency in patients presenting with recurrent infections, particularly sinopulmonary infections, despite having normal total IgG levels. The test aids in differential diagnosis, disease monitoring, treatment response assessment, and helps guide clinical decision-making by the treating immunologist or physician.
- Test Code
- 877
- CPT Code
- 82787
- ICD Code
- D89.89
- Price
- ₹9,000
- Sample Type
- Serum
- Result Time
- Same-day reports are available for samples received Monday or Thursday by 4:00 PM at the laboratory.
- Fasting Required
- Yes (8 hours)
- Method
- Nephelometry
Sample Collection
Overnight fasting (8-12 hours) is preferred before sample collection. Inform your physician about any medications, immunoglobulin therapy, or recent blood transfusions. No special dietary restrictions are required beyond fasting.
Method: Venipuncture
Laboratory Analysis
A trained phlebotomist will collect approximately 2 mL of venous blood from a vein in your arm using standard venipuncture technique. The blood is drawn into a Serum Separator Tube (SST). The procedure typically takes 5-10 minutes and may cause minimal discomfort.
Report Delivery
Apply gentle pressure to the puncture site with a cotton ball for 3-5 minutes. A small bruise may appear at the collection site, which usually resolves within a few days. You may resume normal activities and your regular diet immediately after sample collection.
Timeline: Same-day reports are available for samples received Monday or Thursday by 4:00 PM at the laboratory.
Patient Instructions
About This Test
Who Should Get This Test
The purpose of the Immunoglobulin IgG Subclass 4 Test is to measure the concentration of IgG4 antibodies in the blood. This test serves two primary clinical purposes: (1) to diagnose IgG4-related disease (IgG4-RD), a chronic inflammatory condition characterized by elevated serum IgG4 levels and tissue infiltration by IgG4-positive plasma cells, and (2) to identify selective IgG4 subclass deficiency in patients presenting with recurrent infections, particularly sinopulmonary infections, despite having normal total IgG levels. The test aids in differential diagnosis, disease monitoring, treatment response assessment, and helps guide clinical decision-making by the treating immunologist or physician.
How to Prepare
- Overnight fasting (8-12 hours) is preferred before sample collection
- Inform the phlebotomist about any current medications or immunoglobulin therapy
- Stay well-hydrated before the blood draw
- Wear loose-fitting sleeves for easy access to the arm
- Report any history of bleeding disorders or use of blood-thinning medications
Doctor's Notes
"IgG4 subclass testing is particularly valuable in patients who present with recurrent infections yet have normal total IgG levels. Measuring IgG4 specifically helps identify selective IgG subclass deficiency and is also an essential biomarker for diagnosing IgG4-related disease, a chronic fibro-inflammatory condition that can affect multiple organs. If IgG4 levels are elevated significantly above 135 mg/dL along with characteristic organ involvement, further workup including biopsy with immunostaining should be considered. Equally, very low IgG4 levels may indicate a subclass-specific immunodeficiency that predisposes patients to sinopulmonary infections. I recommend this test when total immunoglobulin panels are normal but clinical suspicion of immune dysregulation remains high."
Test Parameters & Specifications
Sample Stability
- Hemolyzed or severely lipemic samples
- Samples collected in incorrect anticoagulant tubes
- Samples without proper labeling or identification
- Clotted samples in EDTA tubes
- Samples exceeding stability limits at the time of receipt
Understanding Your Results
IgG4 levels are within the normal reference range. In patients with high clinical suspicion of IgG4-related disease, normal levels do not fully exclude the diagnosis, as up to 30-40% of confirmed cases may have normal serum IgG4. Further investigation may still be warranted.
Status: Normal
Range: 3–201 mg/dL
Elevated serum IgG4 is a characteristic finding in IgG4-related disease. However, elevated levels can also be seen in allergic conditions, chronic infections, certain malignancies, and other autoimmune diseases. Clinical, radiological, and biopsy correlation is essential for definitive diagnosis.
Status: Elevated (Suggestive of IgG4-RD)
Range: > 135 mg/dL
Very low IgG4 levels may indicate selective IgG4 subclass deficiency. While isolated IgG4 deficiency is relatively uncommon and its clinical significance is debated, it may contribute to recurrent sinopulmonary infections. Total IgG and other subclass levels should be evaluated concurrently.
Status: Very Low / Deficient
Range: < 3 mg/dL
Consult your doctor if your IgG4 levels are elevated above 135 mg/dL, especially if you are experiencing symptoms such as unexplained organ swelling, abdominal pain, jaundice, fatigue, or weight loss. Also consult if IgG4 levels are very low and you experience frequent or recurrent infections. Any abnormal result should be discussed with your physician or immunologist for appropriate follow-up and further evaluation.
Limitations
- ⚠Serum IgG4 levels alone cannot confirm IgG4-related disease; clinical, radiological, and histopathological correlation is essential
- ⚠Approximately 30-40% of patients with biopsy-proven IgG4-RD may have normal serum IgG4 levels
- ⚠Elevated IgG4 is not specific to IgG4-RD and can be seen in allergic diseases, infections, and other autoimmune conditions
- ⚠This test measures total IgG4 concentration and does not assess IgG4 functionality or specific antibody activity
- ⚠Reference ranges may vary slightly between laboratories and assay platforms
Risks & Considerations
- ●Minor bruising or discomfort at the venipuncture site
- ●Slight risk of infection at the needle insertion point
- ●Rare possibility of fainting or dizziness during blood draw
- ●Very rare hematoma formation at the collection site
Interfering Factors
- ●Recent immunoglobulin therapy or blood transfusion may alter IgG4 levels
- ●Corticosteroid or immunosuppressive therapy can lower IgG4 concentrations
- ●Acute infection or inflammatory states may transiently affect subclass distribution
- ●Polyclonal B-cell activation may cause non-specific elevation of IgG subclasses
- ●Hemolyzed or lipemic samples may interfere with nephelometric measurement
Compare With Similar Tests
| Test | Immunoglobulin IgG Subclass 4 Test | IgG Subclass 1 Test | IgG Subclass 2 Test | IgG Subclass 3 Test | Total IgG Test |
|---|---|---|---|---|---|
| Comparison | Immunoglobulin IgG Subclass 4 Test |
Frequently Asked Questions
What is the Immunoglobulin IgG Subclass 4 Test?
Why is the IgG4 Subclass Test important?
What is a normal IgG4 level?
What does it mean if my IgG4 levels are elevated?
What does it mean if my IgG4 levels are very low?
What are the symptoms of IgG4-related disease?
Is fasting required for the IgG4 Subclass Test?
How is the IgG4 Subclass Test performed?
What is the cost of the IgG4 Subclass Test at DNA Labs India?
How long does it take to get the IgG4 test results?
Can I get home sample collection for this test?
Is the IgG4 test alone sufficient to diagnose IgG4-related disease?
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