Corrected Reticulocyte Count (CRC) and RPI Calculator

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The percentage of red blood cells identified as reticulocytes on the CBC differential. Typical normal range: 0.5-2.5%.
%
The measured hematocrit (packed cell volume) from the patient's blood work.
%
Reference hematocrit for the patient's sex and age. Common defaults: 45% for adult males, 41% for adult females.
%
Red blood cell count from the CBC. Used to calculate the absolute reticulocyte count. Leave at 0 to skip ARC.
x10¹²/L
Corrected Reticulocyte CountHypoproliferative
2.18%

Reticulocyte% adjusted for the degree of anemia

Reticulocyte Production Index1.45
Absolute Reticulocyte Count109x10⁹/L
Maturation correction factor1.5
1.45
Hypoproliferative<2Adequate2-3Hyperproliferative3+

RPI of 1.45 is below 2, an inadequate (hypoproliferative) marrow response, though at the milder end of that range.

  • An RPI between 1 and 2 still sits below the 2.0 threshold for an adequate response: the marrow is producing reticulocytes, but not fast enough for the degree of anemia.
  • Consider mixed-cause anemia: a co-existing nutritional deficiency (iron, B12, folate) or early marrow suppression layered on a peripheral component.
  • Hematocrit of 28% triggers a maturation correction factor of 1.5, accounting for the longer survival of stress reticulocytes in circulation.
  • Absolute reticulocyte count of 109 x10⁹/L is elevated (reference: 20-100 x10⁹/L).

Next stepRequest iron studies, serum B12, and folate. Consider bone marrow biopsy if the cause remains unclear.

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