Hematology / CBC
Haptoglobin
Acute-phase protein that binds free hemoglobin; falls in intravascular hemolysis.
Sample
Serum
Clinical reference range
30 to 200 mg/dL
Adult
Conv: 30–200 mg/dL
Biology
What it measures
Hepatic α2-glycoprotein. Free Hb released by lysed RBCs is bound and cleared by the reticuloendothelial system, depleting haptoglobin.
Clinical use
Why we order it
Hemolysis workup (with LDH ↑, indirect bilirubin ↑, reticulocytes ↑, schistocytes).
Differential
Causes of abnormal values
Causes of HIGH
- ↑Acute-phase response (can mask hemolysis when both processes coexist)
Causes of LOW
- ↓Intravascular hemolysis (TTP, HUS, mechanical valves, AIHA, transfusion reaction)
- ↓Severe liver disease
- ↓Congenital ahaptoglobinemia (~1% prevalence)
Pitfalls
Pre-analytic & interpretation traps
- !As an acute-phase reactant, can be falsely 'normal' during inflammation despite ongoing hemolysis.
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