From the Guidelines
Haptoglobin is a marker for hemolysis, particularly in conditions involving the breakdown of red blood cells. As indicated in a study published in the American Journal of Hematology in 2019 1, haptoglobin is listed among general markers of chronic hemolytic anemia, alongside other indicators such as reticulocytes, bilirubin, and hemoglobin. When red blood cells rupture, they release hemoglobin into the bloodstream, and haptoglobin binds to this free hemoglobin, forming a complex that is then cleared by the liver. As a result, during hemolytic events, haptoglobin levels in the blood decrease significantly because it's being consumed in this clearance process. Some key points about haptoglobin include:
- It can indicate conditions such as autoimmune hemolytic anemia, sickle cell disease, transfusion reactions, or mechanical heart valve hemolysis when its levels are low.
- Haptoglobin can also function as an acute phase protein, meaning its levels may increase during inflammation, infection, or tissue damage.
- Normal haptoglobin levels typically range from 30-200 mg/dL, though reference ranges may vary between laboratories.
- Haptoglobin testing is often used alongside other markers like lactate dehydrogenase (LDH) and reticulocyte count to evaluate suspected hemolysis, as seen in the context of diagnosing conditions like pyruvate kinase deficiency 1.
From the Research
Haptoglobin as a Marker
- Haptoglobin is a marker for hemolysis, as decreased levels of haptoglobin indicate the presence of large amounts of free hemoglobin in the blood 2.
- It is used as a laboratory marker for the diagnosis of hemolytic anemia, as it binds to the globin portion of free hemoglobin 3.
- Low haptoglobin levels, along with other indicators such as low hemoglobin and high total bilirubin, can lead to the diagnosis of autoimmune hemolytic anemia (AIHA) 4.
- Decreased haptoglobin levels are also a confirmatory laboratory test result for hemolysis, along with reticulocytosis, increased lactate dehydrogenase, and increased unconjugated bilirubin 5.
- The protein-protein association between haptoglobin and hemoglobin is extraordinary strong, and the complex formed has clinical potential for modulating inflammatory reactions and functioning as an Hb-based oxygen carrier 6.
Clinical Applications
- Haptoglobin testing can be used to evaluate hemolysis in recently transfused patients, as serum haptoglobin levels can be measured to assess hemolysis 3.
- The test can be used in combination with other factors to validate the diagnosis of hemolysis, as there is no single gold standard for hemolysis 2.
- Haptoglobin can be potentially used as a marker protein for various pathological conditions, as several disorders modify the glycan compositions of haptoglobin 6.