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Calculator: Reticulocyte Production Index (RPI) in adults

Calculator: Reticulocyte Production Index (RPI) in adults


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  • The Maturation term represents the maturation time of red blood cells (in days) at various levels of anemia.
    • Maturation = 1.0 for Hct ≥40%.
    • Maturation = 1.5 for Hct 30 to 39.9%.
    • Maturation = 2.0 for Hct 20 to 29.9%.
    • Maturation = 2.5 for Hct <20%.
  • An RPI >3 shows a normal marrow response to anemia. An RPI <2 is an inadequate response to anemia.
  • With a normal H&H, an RPI of 1 is normal.
  • Hct: hematocrit; Retic: reticulocyte; H&H: hemoglobin and hemotocrit.

Equations used
RPI = (Hct / 45) * Retic / Maturation


  1. Hutchinson RE, Davey FR. Hematopoiesis. In: Clinical Diagnosis and Management by Laboratory Methods, 19th ed, Henry JB (Ed) WB Saunders 1996.
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