From the Guidelines
In hemolytic anemia, the most significant laboratory elevations include lactate dehydrogenase (LDH), indirect (unconjugated) bilirubin, and reticulocyte count, as evidenced by studies such as 1 and 1. These elevations are a result of the breakdown of red blood cells, which leads to the release of LDH, and the liver's processing of increased hemoglobin, resulting in elevated indirect bilirubin. The reticulocyte count increases as the bone marrow responds to anemia by releasing immature red blood cells. Some key laboratory findings in hemolytic anemia include:
- Elevated lactate dehydrogenase (LDH) due to the release from damaged red blood cells during hemolysis, as noted in 1
- Increased indirect (unconjugated) bilirubin as the liver processes the increased hemoglobin from destroyed red cells
- Elevated reticulocyte count as the bone marrow responds to anemia by releasing immature red blood cells
- Decreased haptoglobin, which binds free hemoglobin, as seen in 1
- Elevated urobilinogen in urine
- Sometimes, hemoglobinemia and hemoglobinuria in severe cases
- Complete blood count typically shows decreased hemoglobin and hematocrit
- Peripheral blood smear may reveal spherocytes, schistocytes, or other abnormal red cell morphologies depending on the specific cause of hemolysis, as discussed in 1. These laboratory findings collectively help diagnose hemolytic anemia and distinguish it from other types of anemia, with the pattern of elevation helping to determine whether the hemolysis is intravascular or extravascular.
From the Research
Laboratory Findings in Hemolytic Anemia
The following laboratory tests are typically elevated in hemolytic anemia:
- Reticulocytosis, indicating a compensatory increase in red blood cell production 2, 3, 4, 5
- Lactate dehydrogenase (LDH), a marker of intravascular hemolysis 2, 3, 4, 5
- Unconjugated bilirubin, resulting from the breakdown of red blood cells 2, 3, 4, 5
- Decreased haptoglobin levels, as haptoglobin binds to free hemoglobin in the blood 2, 3, 4, 5
Additional Laboratory Tests
Other laboratory tests that may be useful in diagnosing hemolytic anemia include:
- Direct antiglobulin test (DAT), to differentiate between immune and non-immune causes of hemolysis 2, 3, 5
- Peripheral blood smear, to identify abnormal red blood cell morphologies 2, 3, 4
- Hemoglobin levels, to assess the severity of anemia 3, 5
- Reticulocyte count, to evaluate the bone marrow's response to hemolysis 3, 5