Health Encyclopedia

Quantitative immunoglobulins - nephelometry

Definition

Quantitative nephelometry is a test to quickly and accurately measure the specific level of certain proteins called immunoglobulins in your blood. Specifically, it looks for the proteins IgM, IgG, and IgA.

How the test is performed

Blood is drawn from a vein on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the band is removed to restore blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test

You may be asked not to eat or drink anything for 4 hours before the test.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

The test provides a rapid and accurate measurement of the amounts of the immunoglobulins M, G, and A. Immunoglobulins are proteins that are mostly antibodies.

Normal Values

IgG: 560 to 1800 mg/dL
IgM: 45 to 250 mg/dL
IgA: 100 to 400 mg/dL

What abnormal results mean

Increased levels of IgG may indicate the following:

Decreased levels of IgG may indicate the following:

Increased levels of IgM may indicate the following:

Early HIV infection
Infectious mononucleosis
Lymphosarcoma
Macroglobulinemia
Rheumatoid arthritis

Decreased levels of IgM may indicate the following:

Agammaglobulinemia (very rare)
Amyloidosis
Leukemia
IgM or IgA myeloma

Increased levels of IgA may indicate the following:

Chronic infections, especially involving the gastrointestinal tract
Inflammatory bowel disease
Rheumatic fever

Decreased levels of IgA may indicate the following:

Agammaglobulinemia (very rare)
Hereditary IgA deficiency
Protein-losing gastroenteropathy

What the risks are

Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins

Special considerations

Nephelometry determines the total amount of each immunoglobulin but cannot distinguish antibodies. Other tests such as immunoelectrophoresis or immunofixation can be used to make these distinctions.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

References

McPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:40-1.

Adkinson Jr. NF, Yunginger JW, Busse WW, et al.eds. Middleton's Allergy: Principles and Practice. 6th ed. Philadelphia, Pa: Mosby; 2003:615-16.

Review Date:3/8/2007
Reviewed By:Mark Levin, MD, Hematologist and Oncologist, Newark, NJ. Review provided by VeriMed Healthcare Network.

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