How to diagnose autoimmune hemolytic anemia
How to diagnose autoimmune hemolytic anemia Diagnosing autoimmune hemolytic anemia (AIHA) involves a systematic approach that combines clinical evaluation with laboratory testing to confirm the presence of immune-mediated destruction of red blood cells. Since AIHA can present with symptoms similar to other causes of anemia, accurate diagnosis is crucial for appropriate management.
The initial step involves taking a detailed medical history and performing a thorough physical examination. Patients may report symptoms such as fatigue, pallor, shortness of breath, jaundice, dark urine, and an enlarged spleen. Identifying any underlying conditions, such as autoimmune disorders, infections, or exposure to certain medications, is also important, as these can be associated with AIHA.
Laboratory investigations are central to the diagnosis. The cornerstone test is the complete blood count (CBC), which typically reveals anemia characterized by low hemoglobin levels, often accompanied by a reticulocytosis—an increased number of reticulocytes indicating the bone marrow’s response to red cell destruction. A peripheral blood smear is examined to look for features like spherocytes, schistocytes, or other abnormal red cell shapes, which can provide clues about hemolysis.
A key diagnostic test for AIHA is the direct antiglobulin test (DAT), also known as the Coombs test. This assay detects antibodies or complement proteins bound to the surface of red blood cells. A positive DAT confirms that there is an immune component to the hemolysis. The test can be further refined by identifying whether the antibodies are warm or cold agglutinins, which determines the type of AIHA and guides treatment strategies.
Additional laboratory evaluations include measuring serum bilirubin, which is often elevated due to the breakdown of hemoglobin, and lactate dehydrogenase (LDH), which increases in hemolysis. Serum haptoglobin levels tend to decrease as it binds free hemoglobin relea
sed during red blood cell destruction, serving as another marker of hemolysis. Elevated indirect (unconjugated) bilirubin is also common.
Bone marrow examination may be performed in some cases to assess the marrow’s response to anemia and rule out other hematologic conditions. It typically shows erythroid hyperplasia, reflecting increased red cell production in response to anemia.
In certain cases, additional tests such as cold agglutinin titers, hemolysin titers, and antibody specificity tests are performed to identify the precise immune mechanisms involved. These tests aid in differentiating between warm and cold AIHA, which have different pathophysiologies and treatment approaches.
In summary, diagnosing AIHA requires a combination of clinical suspicion, laboratory evidence of hemolysis, and confirmation of immune involvement through the Coombs test. Recognizing these features promptly allows for early intervention, which is essential for preventing complications and tailoring effective therapy.
