From the Guidelines
Haptoglobin is a crucial marker for identifying hemolysis, and its levels should be interpreted in conjunction with other laboratory tests, such as reticulocyte count, lactate dehydrogenase (LDH), and bilirubin, to determine the presence and severity of red blood cell destruction. When measured in a blood test, low haptoglobin levels typically indicate that red blood cells are being destroyed within the bloodstream, as haptoglobin binds to free hemoglobin released during red cell destruction, and these complexes are rapidly cleared from circulation, depleting haptoglobin levels 1. Normal haptoglobin levels generally range from 30-200 mg/dL, though reference ranges may vary between laboratories. Low or undetectable levels are seen in conditions like autoimmune hemolytic anemia, sickle cell disease, transfusion reactions, and certain medications that cause hemolysis, as outlined in the diagnostic work-up for immune-related adverse events in patients treated with immune checkpoint inhibitor therapy 1. Conversely, haptoglobin is an acute phase reactant that increases during inflammation, infection, or tissue damage. Therefore, normal haptoglobin levels in the presence of suspected hemolysis may indicate concurrent inflammation masking the expected decrease. The diagnostic work-up for hemolytic anemia should consider haptoglobin levels, along with other markers, to establish a diagnosis and guide treatment, as recommended in the management of immune-related adverse events in patients treated with immune checkpoint inhibitor therapy 1. In cases of suspected pyruvate kinase deficiency, haptoglobin levels should be evaluated in conjunction with other laboratory tests, such as reticulocyte count and lactate dehydrogenase (LDH), to determine the presence and severity of hemolysis 1. Overall, haptoglobin testing is a valuable tool in the diagnosis and management of hemolytic anemia, and its interpretation should be guided by the most recent and highest-quality evidence.
From the Research
Haptoglobin and Its Functions
- Haptoglobin is a protein that binds to free hemoglobin in the blood, preventing its toxic effects 2, 3, 4, 5
- It is primarily produced in the liver and plays a crucial role in removing free hemoglobin from the bloodstream 3, 4
- Haptoglobin levels can be used as a marker for hemolysis, with decreased levels indicating hemolysis 2, 3
Haptoglobin and Hemolysis
- Haptoglobin binds to free hemoglobin, preventing its oxidative effects and promoting its removal from the bloodstream 4, 5
- In cases of hyper-hemolytic conditions or chronic hemolysis, haptoglobin is depleted, allowing free hemoglobin to distribute to tissues and cause damage 4
- Haptoglobin administration has been shown to reduce plasma-free hemoglobin levels and preserve kidney function in patients with hemolysis 6
Clinical Usefulness of Haptoglobin
- Haptoglobin levels can be used to diagnose hemolytic anemia and evaluate hemolysis in recently transfused patients 2
- Haptoglobin testing can be used to assess hemolysis, but interpretation can be difficult in certain settings, such as inflammation 3
- Haptoglobin derivatives are being developed for the prevention of hemoglobin toxicity in hemolytic diseases such as sickle cell disease 5