IMMUNOGLOBULIN G (IgG) TEST - THE IMMUNITY MARKER
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Report Time: Next Day Evening | Sample: Blood (Serum) | Processing: Except Sunday
Immunoglobulin G (IgG) is the most abundant and important antibody in your blood, making up about 75-80% of your total antibodies. It acts as the Memory Bank of your immune system, remembering every infection and vaccination you have ever had to protect you from future attacks.
What is Immunoglobulin G (IgG)?
Your immune system is an intelligent defense network. When a virus or bacteria enters your body for the first time, your system creates immediate fighters (IgM). But once the battle is won, your body needs to remember the enemy in case it returns. That is the job of IgG.
Produced by B-lymphocytes (plasma cells), IgG antibodies circulate in your blood, lymph fluid, and tissues. They have a Y shape that allows them to lock onto specific antigens (germs) and neutralize them or flag them for destruction by other white blood cells.
Why is the IgG Test Performed?
Doctors prescribe the IgG test for a variety of diagnostic reasons, ranging from checking immunity to diagnosing cancer. Here are the main clinical indications:
1. Evaluating Immunity & Vaccine Response
IgG levels tell us if you are immune to a specific disease. Doctors check IgG titers for:
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✔Rubella, Measles, Mumps: Especially during pregnancy planning to ensure the mother is immune.
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✔Hepatitis B & Varicella (Chickenpox): To check if a vaccine (like the Hep B shot) worked effectively.
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✔COVID-19: To see if you have developed antibodies after an infection or vaccination.
2. Diagnosing Chronic Infections
While IgM indicates a new infection, high IgG levels indicate a chronic (ongoing) or past infection. If IgG levels are rising over time (4-fold rise), it suggests an active reinfection or reactivation (like in Herpes or Cytomegalovirus).
3. Investigating Autoimmune Diseases
In autoimmune conditions, the body gets confused and makes IgG antibodies that attack healthy tissues. High IgG levels (Polyclonal Gammopathy) are classic signs of:
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➤Systemic Lupus Erythematosus (SLE)
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➤Rheumatoid Arthritis (RA)
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➤Sjogren’s Syndrome
4. Detecting Multiple Myeloma
Multiple Myeloma is a cancer of the plasma cells. In this condition, the cells produce an uncontrolled amount of useless, monoclonal IgG. A very high IgG level (e.g., >2000-3000 mg/dL) is a major red flag for Myeloma or MGUS (Monoclonal Gammopathy of Undetermined Significance).
5. Diagnosing Immunodeficiency (CVID)
If you get sick frequently with sinus infections, bronchitis, or pneumonia, you may have Hypogammaglobulinemia (Low IgG). Common Variable Immunodeficiency (CVID) is a condition where the body cannot make enough IgG, leaving you vulnerable to bacteria.
The 4 Subclasses of IgG
IgG isn't just one thing; it's a family of four. Sometimes, your Total IgG can be normal, but you might be missing one specific type, leading to illness. This requires a specialized IgG Subclass test, but understanding them is important:
| Subclass | Primary Function | Deficiency Symptoms |
|---|---|---|
| IgG1 (60-70%) | Fighting viral and bacterial proteins (tetanus, diphtheria). | Severe, general recurrent infections. |
| IgG2 (20-30%) | Fighting bacteria with polysaccharide capsules (Pneumococcus, H. flu). | Recurrent sinus/ear infections & pneumonia. |
| IgG3 (5-8%) | Activates the complement system (a powerful immune response). | Frequent respiratory infections. |
| IgG4 (1-4%) | Regulates allergic responses; linked to IgG4-Related Disease. | Often asymptomatic deficiency; Excess causes organ fibrosis. |
Interpreting Your Results
Your results will show a number in mg/dL. Here is what high or low levels typically mean:
High IgG Levels (Hypergammaglobulinemia)
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➤Polyclonal (Broad increase): Indicates the immune system is stimulated by chronic infection (HIV, Hepatitis), liver disease (Cirrhosis), or autoimmune disorders (Lupus).
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➤Monoclonal (Sharp spike): Indicates a single clone of cells is overproducing. This is the hallmark of Multiple Myeloma, Waldenstrom’s, or MGUS.
Low IgG Levels (Hypogammaglobulinemia)
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➤Protein Loss: Conditions like Nephrotic Syndrome (kidney disease) or protein-losing enteropathy cause IgG to leak out of the body in urine or stool.
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➤Production Failure: Genetic diseases (CVID, Agammaglobulinemia) or bone marrow suppression from chemotherapy.
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➤Medications: Drugs like Rituximab, Steroids, and certain anti-seizure meds can suppress IgG production.
IgG vs. IgM: What’s the Difference?
This is the most common confusion among patients. Here is the simple breakdown:
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✔IgM = I have it NOW. (Active Infection)
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✔IgG = I had it BEFORE. (Past Infection or Immunity)
For example, in a Dengue or Rubella test:
Positive IgM, Negative IgG: You are sick right now.
Negative IgM, Positive IgG: You had it in the past and are now immune (safe).
Preparation & Procedure
The IgG test is a simple procedure with minimal requirements:
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✔Fasting: No fasting is required. You can eat and drink normally.
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✔Medications: Inform your doctor if you are taking steroids (Prednisone), immunosuppressants, or have had a recent vaccination (within 4 weeks), as these can influence levels.
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✔Sample: A small amount of blood is drawn from a vein in your arm.
Frequently Asked Questions (FAQs)
If your low IgG is due to malnutrition, a balanced diet with protein can help. However, if it is due to a genetic condition (CVID), diet alone cannot fix it. You may require Immunoglobulin Replacement Therapy (IVIG), which involves infusions of antibodies from healthy donors.
Doctors test IgG (TORCH panel) to see if the mother is immune to diseases like Rubella and Toxoplasmosis. If she has IgG (immunity), the baby is protected. If she lacks IgG, she must avoid exposure during pregnancy to prevent birth defects.
At Sanovra Lab, the report is generated by the Next Day Evening after sample collection.
Not always. A mild elevation often just means your body is fighting a chronic infection or inflammation. However, extremely high levels (Monoclonal spike) can damage the kidneys and thicken the blood, requiring urgent medical evaluation for Myeloma.
No, the IgG test is processed on all days Except Sunday.
Check Your Long-Term Immunity
Whether for vaccine verification, chronic illness, or general health, get accurate IgG testing at Sanovra Lab.
Disclaimer: The information provided here is for educational purposes only and does not constitute medical advice. Laboratory results should always be interpreted by a qualified Doctor in the context of clinical findings.