From the Guidelines
Blood tests for hemolysis should include lactate dehydrogenase (LDH), haptoglobin, reticulocyte count, bilirubin levels, and peripheral blood smear examination, as recommended by the most recent guidelines 1. These tests are essential for diagnosing and managing hemolysis, as they help identify the underlying cause and guide treatment.
Key Tests for Hemolysis
- LDH: elevated during hemolysis as it's released from damaged red blood cells
- Haptoglobin: depleted during hemolysis as it binds free hemoglobin
- Reticulocyte count: increases as the bone marrow responds to red cell destruction
- Bilirubin levels: rise due to increased red cell breakdown, with unconjugated bilirubin being a key indicator
- Peripheral blood smear examination: may show fragmented red cells (schistocytes), spherocytes, or other abnormal morphologies depending on the cause of hemolysis Additional useful tests include:
- Direct antiglobulin test (Coombs test) to detect antibody-mediated hemolysis
- Hemoglobin electrophoresis for hemoglobinopathies
- Tests for G6PD deficiency or other enzyme deficiencies These tests help differentiate between intravascular hemolysis (occurring within blood vessels) and extravascular hemolysis (occurring in the spleen or liver), which guides appropriate treatment 1.
Importance of Hemolysis Testing
Hemolysis testing is crucial for diagnosing conditions like autoimmune hemolytic anemia, hereditary spherocytosis, and microangiopathic hemolytic anemias, and for guiding treatment to improve patient outcomes and reduce morbidity and mortality 1. The most recent guidelines from 2021 1 provide the best evidence for the diagnostic workup of hemolysis, and should be followed in clinical practice to ensure optimal patient care.
From the Research
Blood Tests for Haemolysis
- Laboratory tests that confirm haemolysis include:
- Reticulocytosis
- Increased lactate dehydrogenase
- Increased unconjugated bilirubin
- Decreased haptoglobin levels 2
- The direct antiglobulin test can further differentiate immune causes from nonimmune causes of haemolysis 2
- A peripheral blood smear should be performed when haemolysis is present to identify abnormal red blood cell morphologies 2
Classification of Haemolytic Diseases
- Haemolytic diseases are classified into:
- Hemoglobinopathies
- Membranopathies
- Enzymopathies
- Immune-mediated anemias
- Extrinsic nonimmune causes 2
- Extrinsic nonimmune causes include:
- Thrombotic microangiopathies
- Direct trauma
- Infections
- Systemic diseases
- Oxidative insults 2