From the Guidelines
A positive Coombs test is a strong indicator of an immune-mediated hemolysis, suggesting the presence of antibodies attached to red blood cells or in the serum, and requires further investigation to determine the underlying cause. The direct Coombs test detects antibodies already bound to red blood cells, while the indirect test identifies antibodies in the serum that can bind to red blood cells. This test is commonly used to diagnose autoimmune hemolytic anemia, hemolytic disease of the newborn, transfusion reactions, and drug-induced hemolytic anemia. In the context of chronic lymphocytic leukemia (CLL) or non-Hodgkin’s lymphoma, a positive Coombs test may indicate autoimmune hemolytic anemia, which is a known complication of these conditions 1. According to the 2015 guidelines for CLL, a direct Coombs’ test should be performed in patients with anemia to evaluate for the possibility of hemolysis and pure red aplasia 1. Key points to consider when interpreting a positive Coombs test include:
- The presence of antibodies against red blood cells, which can lead to hemolysis
- The need for further investigation to determine the underlying cause of the positive test result
- The potential for autoimmune hemolytic anemia, particularly in patients with CLL or non-Hodgkin’s lymphoma
- The importance of medication review, additional blood tests, and clinical evaluation to determine the cause of the positive Coombs test. In clinical practice, a positive Coombs test should prompt a thorough evaluation to identify the underlying cause of the immune-mediated hemolysis, and guide treatment decisions to improve patient outcomes.
From the Research
Positive Coombs Test Indications
A positive Coombs test, also known as a direct antiglobulin test (DAT), indicates the presence of antibodies or complement proteins that are bound to the surface of red blood cells [ 2, 3, 4, 5 ]. This can lead to the destruction of red blood cells, resulting in hemolytic anemia.
Causes of Positive Coombs Test
The causes of a positive Coombs test can vary, including:
- Autoimmune hemolytic anemia (AIHA), where the immune system produces antibodies against the person's own red blood cells [ 2, 3, 4 ]
- Infections, such as cytomegalovirus (CMV) or Epstein-Barr virus (EBV) [ 2 ]
- Certain medications, such as penicillin or cephalosporins [ 2 ]
- Underlying medical conditions, such as ulcerative colitis or Hodgkin's disease [ 4, 5 ]
- Non-Hodgkin's lymphoma [ 6 ]
Clinical Significance
A positive Coombs test can have significant clinical implications, including:
- Diagnosis of autoimmune hemolytic anemia or other underlying medical conditions
- Identification of potential causes of hemolytic anemia, such as infections or medications
- Guidance for treatment, such as immunosuppressive therapy or splenectomy
- Monitoring of disease progression or response to treatment [ 2, 3, 4, 5, 6 ]