| Subject | Contents |
| Definition | A test that measures the level of febrile or cold agglutinins in blood. Agglutinins are antibodies that cause the red blood cells to gather together at low (cold) or high (febrile) temperatures. |
| Alternative Names | Cold agglutinins; Weil-Felix reaction; Widal's test |
| How the test is 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. The sample is collected in a tube that has been warmed to normal body temperature (98.6 degrees F) and sent to a laboratory. |
| How to prepare for the test | Adults: There is no special preparation. 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) schoolage 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 antibodies appear in the blood after infections by a variety of microorganisms. A positive test for cold agglutinins can indicate atypical pneumonia or viral infections. |
| Normal Values | febrile (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 febrile agglutinins may occur after:brucellosisrickettsial diseasesalmonella infectiontularemia The presence of cold agglutinins may occur after: infectious mononucleosisinfluenzaatypical pneumoniamultiple myelomaMycoplasma pneumoniae infectionscleroderma staphylococcemia ( septicemia with staphylococcus bacteria)cytomegalovirus infectionhemolytic anemiamalariacirrhosis congenital syphilisperipheral vascular diseasepulmonary embolism trypanosomiasis tonsillitisscarlatina idiopathic cold agglutinin disease |
| What the risks are | excessive bleedingfainting 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. |
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