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.

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.

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

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.

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.

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

Increased levels of IgG may indicate the following:

• Chronic infection
• Hyperimmunization
• IgG multiple myeloma
• Liver disease
• Rheumatic fever
• Rheumatoid arthritis

• Agammaglobulinemia (very rare)
• Amyloidosis
• Leukemia
• Preeclampsia

• Early HIV infection
• Infectious mononucleosis
• Lymphosarcoma
• Macroglobulinemia
• Rheumatoid arthritis

• Agammaglobulinemia (very rare)
• Amyloidosis
• Leukemia
• IgM or IgA myeloma

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

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

• 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

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.

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.