|
Febrile/cold agglutinins
Definition
Agglutinins are antibodies that cause the red blood cells to clump together.
- Cold agglutinins are active at cold temperatures.
- Febrile (warm) agglutinins are active at normal body temperatures.
This article discusses the blood test used to measure the level of these antibodies in the blood.
Alternative Names
Cold agglutinins; Weil-Felix reaction; Widal's test; Warm agglutinins; Agglutinins
How the Test is Performed
A blood sample is needed. For information on how this is done, see: Venipuncture
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 can direct therapy.
Normal Results
- Warm agglutinins: no agglutination in titers at or below 1:80
- Cold agglutinins: no agglutination in titers at or below 1:16
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
An abnormal (positive) result means there were agglutinins in the blood sample.
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
Cold agglutinins may occur with:
- Infections, especially mononucleous and Mycoplasma pneumonia
- Chicken pox (varicella)
- Cytomegalovirus infection
- Cancer, including lymphoma and multiple myeloma
- Listeria monocytogenes
- Systemic lupus erythematosus
- Waldenstrom macrogolulinemia
Risks
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.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Considerations
If cold agglutinin disease is suspected, the individual needs to be kept warm.
References
Schwartz RS. Autoimmune and intravascular hemolytic anemias. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa:Saunders Elsevier; 2011:chap 163.
Baum SG. Mycoplasma infections. In: Goldman L, Schafer AI,eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 325.
Powers A, Silberstein LE. Autoimmune hemolytic anemia. In: Hoffman R, Benz EJ, Shattil SS, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 47.
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
