The diagnosis of hemolytic anemia can be suspected on the basis of a constellation of symptoms and is largely based on the presence of anemia, an increased proportion of immature red cells (reticulocytes) and a decrease in the level of haptoglobin, a protein that binds free hemoglobin. Examination of a peripheral blood smear and some other laboratory studies can contribute to the diagnosis. Symptoms of hemolytic anemia include those that can occur in all anemias as well as the specific consequences of hemolysis. All anemias can cause fatigue, shortness of breath, decreased ability to exercise when severe. Symptoms specifically related to hemolysis include jaundice and dark colored urine due to the presence of hemoglobin (hemoglobinuria). When restricted to the morning hemoglobinuria may suggest paroxysmal nocturnal haemoglobinuria. Direct examination of blood under a microscope in a peripheral blood smear may demonstrate red blood cell fragments called schistocytes, red blood cells that look like spheres (spherocytes), and/or red blood cells missing small pieces (bite cells). An increased number of newly made red blood cells (reticulocytes) may also be a sign of bone marrow compensation for anemia. Laboratory studies commonly used to investigate hemolytic anemia include blood tests for breakdown products of red blood cells, bilirubin and lactate dehydrogenase, a test for the free hemoglobin binding protein haptoglobin, and the direct Coombs test (also called direct antiglobulin test or DAT) to evaluate complement factors and/or antibodies binding to red blood cells:[48]
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Treatment
Definitive therapy depends on the cause:
- Symptomatic treatment can be given by blood transfusion, if there is marked anemia. A positive Coombs test is a relative contraindication to transfuse the patient. In cold hemolytic anemia there is advantage in transfusing warmed blood.
- In severe immune-related hemolytic anemia, steroid therapy is sometimes necessary.
- In steroid resistant cases, consideration can be given to rituximab or addition of an immunosuppressant (azathioprine, cyclophosphamide).
- Association of methylprednisolone and intravenous immunoglobulin can control hemolysis in acute severe cases.
- Sometimes splenectomy can be helpful where extravascular hemolysis, or hereditary spherocytosis, is predominant (i.e., most of the red blood cells are being removed by the spleen).[49]
Mitapivat was approved for medical use in the United States in February 2022.[50]
Other animals
Hemolytic anemia affects nonhuman species as well as humans. It has been found, in a number of animal species, to result from specific triggers.[51]
Some notable cases include hemolytic anemia found in black rhinos kept in captivity, with the disease, in one instance, affecting 20% of captive rhinos at a specific facility.[52][53][54] The disease is also found in wild rhinos.[55]
Dogs and cats differ slightly from humans in some details of their RBC composition and have altered susceptibility to damage, notably, increased susceptibility to oxidative damage from consumption of onion. Garlic is less toxic to dogs than onion.[56]