Q: At what level of low haptoglobin it is considered due to hemolytic anemia?
Answer: Haptoglobin is an acute-phase reactant which goes up in infection and inflammation. But in clinical practice it is mostly used to predict hemolysis by it's low level. There are other reasons for low heptoglobin such as abdominal trauma and congenital ahaptoglobinemia but if haptoglobin level is less than 25 mg/dL, it is due to hemolysis proved otherwise. This should be read in conjunction with other labs such as high LDH and bilirubin but undetectable or extremely low haptoglobin itself is a good marker to consider hemolysis.
Normal haptoglobin level is 30-200 mg/dL.
1. Marchand A, Galen RS, Van Lente F. The predictive value of serum haptoglobin in hemolytic disease. JAMA 1980; 243:1909.
2. Stahl WM. Acute phase protein response to tissue injury. Crit Care Med 1987; 15:545.