Haptoglobin
Overview
Haptoglobin is a glycoprotein produced by the liver that binds free hemoglobin released during intravascular hemolysis, forming a haptoglobin–hemoglobin complex that is cleared by the reticuloendothelial system. This protects the kidneys from hemoglobin‑induced oxidative damage and prevents iron loss through urine. Low levels usually indicate ongoing intravascular hemolysis, liver disease, or chronic inflammation, whereas high levels occur in infections, malignancy, and other acute‑phase states. Haptoglobin is clinically useful as a marker of hemolytic anemia, especially intravascular hemolysis, and as part of the evaluation of anemia of unknown cause.
Clinical Use Cases
- Investigating suspected intravascular hemolysis (e.g., hemolytic anemia, hemoglobinuria, mechanical heart valves).
- Differentiating intravascular from extravascular hemolysis.
- Supporting diagnosis of anemia in chronic disease (when elevated).
- Monitoring disease activity in some inflammatory and neoplastic conditions.
Specimen Types
- Serum.
- Plasma (less commonly used; serum is preferred).
Measurement Methods
- Immunoassay (immunoturbidimetric or nephelometric).
- Enzyme‑linked immunosorbent assay (ELISA) in some research or reference labs.
- Automated clinical chemistry platforms with standardized haptoglobin assays.
Test Preparation and Influencing Factors
- No specific fasting requirement.
- Recent transfusion or hemolysis before sampling can lower serum haptoglobin.
- Liver disease (e.g., cirrhosis) and severe malnutrition may reduce haptoglobin production.
- Inflammatory states, pregnancy, and oral contraceptives typically increase haptoglobin because it is an acute‑phase protein.
Synonyms
- Haptoglobin (Hp).
- Haptoglobin‑hemoglobin complex.
- Haptoglobin, serum.