How Performed: Adult or child:
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 air-tight 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.
Nephelometry is a laboratory technique to obtain a measurement of the amount of IgM, IgG, and IgA immunoglobulins accurately and rapidly. It 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 To Prepare: 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 experience, 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:
How It Feels: 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.
Risks:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Why 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: 950 to 1550 mg/dl
- IgM: 75 to 175 mg/dl
- IgA: 160 to 260 mg/dl
Note: mg/dl = milligrams per deciliter
Abnormal Results: Increased levels of IgG may indicate:
Decreased levels of IgG may indicate:Increased levels of IgM may indicate:Decreased levels of IgM may indicate:Increased levels of IgA may indicate:Decreased levels of IgA may indicate:- agammaglobulinemia (very rare)
- protein-losing gastroenteropathy
- hereditary IgA deficiency (1 out of 700 people)
Cost:
Special Considerations: Nephelometry only determines the total amount of each immunoglobulin but cannot distinguish monoclonal antibodies (as can immunoelectrophoresis or immunofixation).
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.
