Health Encyclopedia

Febrile/cold agglutinins

Definition

Agglutinins are antibodies that cause the red blood cells to gather together.

Cold agglutinins are active at cold temperatures.
Febrile (warm) agglutinins are active at normal body temperature.

This article discusses the blood test used to measures the level of these antibodies in the blood.

Alternative Names

Cold agglutinins; Weil-Felix reaction; Widal's test; Warm agglutinins

How the test is performed

Blood is 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 tube is first warmed to normal body temperature - 98.6 degrees F). 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.

The sample is sent to a laboratory.

How to prepare for the test

There is no special preparation.

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

This test is done to diagnose certain infections and to determine the cause of hemolytic anemia. Distinguishing between warm and cold agglutinins can help understand why the hemolytic anemia is occurring and directs therapy.

Normal Values

Warm agglutinins: no agglutination in titers at or below 1:80
Cold agglutinins: no agglutination in titers at or below 1:16

What abnormal results mean

The presence of warm agglutinins may occur with:

Infections, including brucellosis, rickettsial disease, salmonella infection, and tularemia
Lymphoma
Systemic lupus erythematosus
Use of certain medicines, including methyldopa, penicillin, and quinidine

The presence of cold agglutinins may occur with:

Infections, especially Mycoplasma pneumonia
Previous viral, staphylococcal, or malaria infection
Cancer, including lymphoma and multiple myeloma
Systemic lupus erythematosus

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

If cold agglutinin disease is suspected, the individual needs to be kept warm.

Review Date:5/27/2007
Reviewed By:Steve Lee, DO, Rheumatology Fellow, Loma Linda University Medical Center, Loma Linda, CA. Review provided by VeriMed Healthcare Network.

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