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Acute phase protein (Acute Phase Reactants)






  1. This is α-2 glycoprotein and binds Hemoglobin irreversibly.
    1. This is free Hb binding protein. 
    2. This is present in the α-2 zone on electrophoresis. 
  2. This is synthesized in the liver and consists of four peptide chains linked by a disulfide bond.


  1. It binds free hemoglobin and is rapidly cleared from the blood in case of intravascular hemolysis.
    1. In the initial stage of the hemolysis, the liver can compensate for the synthesis of HP, so its level is decreased.

  1. This is increased in acute and chronic inflammation.
  2. It is a natural bacteriostatic agent for iron-requiring bacteria e.g. E.coli.
  3. This is acute phase protein increased in ulcerative colitis, acute rheumatic diseases and heart attack.
  4. This is helpful to differentiate hemolytic anemia from the other causes of anemia.
    1. Haptoglobin is markedly increased plus Reticulocytes are increased indicates intravascular hemolysis.
    2. Haptoglobin is normal or slightly decreased plus Reticulocytes are increased indicate extravascular hemolysis in liver or spleen.
    3. Haptoglobin is normal plus Reticulocytes are not increased indicate decreased production of the RBC from bone marrow.
    4. Haptoglobin depletion is a sensitive marker for the hemolysis.
    5. HP is decreased in the hemoglobinuria.
    6. HP is unchanged in the myoglobinuria and rhabdomyolysis because there is no binding with HP.



The increased  level is seen in:

  1. By corticosteroids hormones and nonsteroidal anti-inflammatory drugs.
  2. In nephrotic syndrome.
  3. In biliary obstruction in absence of hepatocellular disease.
  4. Ulcerative colitis.
  5. peptic ulcer.
  6. Acute rheumatic disease.
  7. In cancers.
  8. In acute and chronic inflammatory disease and it acts as acute phase protein.
  9. In acute myocardial infarction.
  10. In tissue destruction like burn, and cancers.
  11. Drugs that may increase the level are:
    1. Steroids.
    2. Androgens.

The decreased level is seen in:

  1. In hemolytic anemia.
  2. Systemic lupus erythematosus
  3. Erythroblastosis fetalis.
  4. Estrogen will decrease its synthesis.
  5. Decreased with severe liver diseases.
  6. The slight decrease in blood transfusion even in the compatible blood transfusion due to the presence of few RBC hemolysis.
  7. This may be decreased in hematoma because of binding of Hb with HP.
  8. Drugs that may decrease the level are:
    1. Chlorpromazine.
    2. Isoniazid.
    3. Oral contraceptives.
    4. Streptomycin.
    5. Quinidine.
    6. Nitrofurantoin.

Critical value is <40 mg/dL. 


Possible References Used

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