What is the role of CBC count and peripheral smear in the workup of cold agglutinin disease?

Updated: Aug 28, 2018
  • Author: Salman Abdullah Aljubran, MD; Chief Editor: Michael A Kaliner, MD  more...
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If the cold agglutinin is operative at room temperature, then a falsely high mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) with a low RBC count are obtained due to agglutination of RBCs in the cold automated counter.

Agglutination may also be seen in anticoagulated blood at room temperature. This agglutination worsens with storage and cooling of blood to 4°C and disappears rapidly upon warming the blood to 37°C, unlike with rouleaux formation. Repeating the complete blood count (CBC) after warming the blood to 37°C avoids this problem. Thus, the clinical laboratory is frequently the first to report the presence of a cold agglutinin. Agglutination in the cold may also interfere with typing and cross-matching of blood.

In patients with chronic cold agglutinin disease, a mild to moderate stable anemia is present; occasionally, the anemia is severe. Leukocytosis may be evident during hemolytic episodes. Peripheral blood smears may reveal clumps of RBCs (see the image below).

Peripheral blood smear showing several clumps of R Peripheral blood smear showing several clumps of RBCs with the largest in the center. These are typical of aggregates seen in persons with cold agglutinin disease.

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