Definition

Nephelometry is a laboratory technique used to obtain a measurement of the amount of IgM, IgG, and IgA immunoglobulins accurately and rapidly.

The test uses a specialized instrument to measure the movement of particles in a solution (turbidity) caused by the interaction of immunoglobulins in the serum and anti-immunoglobulin that has been added to the serum.

How the test is performed

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (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 tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

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 to fast for 4 hours before the test.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

 
• Infant test or procedure preparation (birth to 1 year)  
• Toddler test or procedure preparation (1 to 3 years)  
• Preschooler test or procedure preparation (3 to 6 years)  
• School age test or procedure preparation (6 to 12 years)  
• Adolescent test or procedure preparation (12 to 18 years)

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 immunoglobulins M, G, and A. (Immunoglobulin D has no known clinical significance, and IgE must be measured by more sensitive techniques such as radioimmunoassay or enzyme-linked immunoassay.)

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:

 
• Chronic infection  
• Hyperimmunization  
• IgG Multiple Myeloma  
• Liver disease  
• Rheumatoid Arthritis  
• Rheumatic fever

Decreased levels of IgG may indicate the following:

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

Increased levels of IgM may indicate the following:

 
• Infectious mononucleosis  
• Lymphosarcoma  
• Macroglobulinemia  
• Rheumatoid Arthritis

Decreased levels of IgM may indicate the following:

 
• Agammaglobulinemia (very rare)  
• Amyloidosis  
• Leukemia

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)  
• Protein-losing gastroenteropathy  
• Hereditary IgA deficiency

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 monoclonal 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.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.