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 typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any 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.
- IgG: 560 to 1800 mg/dL
- IgM: 45 to 250 mg/dL
- IgA: 100 to 400 mg/dL
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
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:
Decreased levels of IgM may indicate the following:
- Agammaglobulinemia (very rare)
Increased levels of IgA may indicate the following:
- Chronic infections, especially involving the gastrointestinal tract
- Inflammatory bowel disease
Decreased levels of IgA may indicate the following:
- Agammaglobulinemia (very rare)
- Hereditary IgA deficiency
- Protein-losing gastroenteropathy
What the risks are:
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Nephelometry determines the total amount of each immunoglobulin but cannot distinguish specific antibodies. Other tests such as immunoelectrophoresis or immunofixation can be used to make these distinctions.
McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006.
Adkinson NF Jr, ed. Middleton’s Allergy: Principles and Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2008.