Unexpected laboratory results in cold agglutinin disease

Cold agglutinin disease (CAD) is an autoimmune hemolytic disease in which antibodies for erythrocyte surface antigens are activated by low temperatures, causing agglutination of erythrocytes. Most of the published cases in the literature are related to the clinical presentation of the disease. Cold agglutinins can also interfere with laboratory tests. In this case, unexpected haptoglobin (Hp) and glycated hemoglobin (HbA1c) results, as well as complete blood count (CBC), were reported. A 55-year-old woman with joint paint presented at the rheumatology polyclinic. Blood samples were collected into anticoagulated and gel separation tubes for CBC, HbA1c, and biochemistry tests. The automated hematology analyzer results indicated a very low hematocrit (7%) and erythrocyte count (0.57x106 mm³). The erythrocyte indices, platelet count, and mean platelet volume could not be measured. Hp was undetectable. The HbA1c value was below the reference threshold. The patient’s file revealed that she had been diagnosed with CAD 5 years earlier. The samples were reanalyzed after warming in a Benmarie for 25 minutes to 37°C. While the CBC results improved, the HbA1c and Hp results did not change. Informing the laboratory when samples to be used are from patients with CAD and providing the proper temperature conditions during transportation will ensure accurate results, as well as decrease workload and laboratory costs.