Definition

Antibodies, also known as immunoglobulins, play a crucial role in defending the body’s immune system. These immunoglobulins are proteins that are produced by immune cells to fight off foreign invaders such as viruses and bacteria. When the body is exposed to these harmful agents, it generates antibodies. IgG antibodies make up around 70-80% of the immunoglobulins present in the blood. These specific antibodies are initially produced when the body is exposed to an infection or antigen, and after a few weeks, their levels rise before gradually decreasing and stabilizing.

The body retains a memory of these IgG antibodies, which allows it to produce them rapidly when re-exposed to the same antigen. This forms the basis for long-term protection against harmful microorganisms. Under normal immune conditions, IgG helps prevent reinfection. Additionally, IgG is the only immunoglobulin that can cross the placenta, providing protection to the fetus during pregnancy and continuing to offer immunity for several months after birth.

IgG antibodies are categorized into four different types:

• IgG1

• IgG2

• IgG3

• IgG4

Indication

A healthcare provider may recommend this test for several reasons, including:

• To help diagnose whether an individual has previously been exposed to a particular disease

• To assess a person's immune response after undergoing treatment for an illness or following vaccination

• To investigate chronic inflammation, recurring infections, or infections believed to be caused by IgG antibodies

Contraindication

There are no specific contraindications for undergoing an IgG test.

Preparation Before the Test

No special preparation is required before the IgG test. Fasting is not necessary for this procedure. However, it’s important to inform your healthcare provider if you are taking any medications or consuming foods that might affect the results. It’s also advisable to remain calm and stay hydrated before the test.

Test Procedure

The IgG test requires a blood sample, which will be collected by a trained lab technician. The technician will first cleanse your arm using sterile alcohol, then draw a small amount of blood from a vein in your arm using a sterile syringe. For infants, blood is typically collected from the heel.

To collect blood from a vein, the skin will be cleaned with an antiseptic and a special band (tourniquet) will be applied around the arm to increase blood flow and cause the vein to swell. The needle will then be inserted into the vein, often in the inner arm, elbow, or back of the hand, and the blood is drawn into a vial or syringe. Afterward, the tourniquet is removed, and the puncture site is covered with a bandage to stop any bleeding.

The collected blood sample is placed into a test tube and analyzed by a lab technician using specialized equipment. The results of the test are usually available within a day. The risks associated with this test are minimal. Some individuals may experience mild discomfort, dizziness, or bruising at the puncture site, but these symptoms typically resolve quickly. The test itself is relatively simple and generally takes no more than 10 minutes to complete.

Normal and Abnormal Values

The normal range for IgG test results varies based on age:

• For infants aged 0 - 1 year, the normal range is between 231 and 1411 mg/dL

• For children aged 1 - 3 years, the normal range is between 453 and 916 mg/dL

• For children aged 4 - 6 years, the normal range is between 504 and 1464 mg/dL

• For children aged 10 - 11 years, the normal range is between 698 and 1560 mg/dL

• For teenagers aged 12 - 13 years, the normal range is between 759 and 1549 mg/dL

• For teenagers aged 14 - 15 years, the normal range is between 716 and 1711 mg/dL

• For individuals aged 16 - 19 years, the normal range is between 549 and 1584 mg/dL

• For adults over the age of 19 years, the normal range is between 700 and 1600 mg/dL

Results and Recommendations (Follow-up Tests)

IgG test results typically cannot provide a full diagnosis on their own, so doctors often recommend additional tests, such as an IgM test, to help ensure a more accurate diagnosis. While IgG testing can offer indications of potential infections or autoimmune disorders, it does not pinpoint the exact cause behind abnormal IgG levels. Therefore, further antibody testing or additional assessments may be required to provide more clarity.

Elevated IgG levels could be a sign of an ongoing infection or an autoimmune condition, suggesting the body’s immune system is actively responding. On the other hand, low IgG levels may indicate protein loss, which can occur due to diseases or traumatic events like burns, or even conditions such as diabetes.

Consult the Right Doctor

If the IgG test results are abnormal, seeking advice from a general practitioner is a good starting point. They can provide a diagnosis and recommend appropriate treatment. In some cases, an internal medicine specialist may be necessary for more specialized care. The doctor might suggest additional tests to confirm the diagnosis and determine the best course of action.

Looking for more information about laboratory, radiology, and other examination results? Click here!