Reticulocyte Production Index (RPI): Calculation & Interpretation

The Reticulocyte Production Index is used to determine if a person's bone marrow is properly responding to the body's need for red blood cells. It's also used to diagnose anemia, a condition wherein a person has a decreased number of red blood cells. The index is actually a percentage calculation because it determines the number of reticulocytes as a percentage of red blood cells.

Things You'll Need

• Calculator

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Instructions

• 1

  Determine the patient's reticulocyte count and hematocrit count through blood tests. As an example, a patient has a reticulocyte count of 3 percent and hematocrit count of 22 percent.

• 2

  Correct for the maturation of prematurely released reticulocytes in the blood stream. This value is represented in days. For hematocrit percentages between 36 and 45, use a maturation correction of one day; for hematocrit percentages between 26 and 35, use a maturation correction of 1.5 days; for hematocrit percentages between 16 and 25, use a maturation correction of two days; and for hematocrit percentages below 16, use a maturation correction of 2.5 days. In the example, because the hematocrit is 22 percent, you would use a maturation correction of two days.

• 3

  Divide the hematocrit count by 45, which is the normal hematocrit level. In the example, you would divide 22 by 45 and get 0.4889.

• 4

  Multiply the result from Step 3 by the patient's reticulocyte count. In the example, you would multiply 3 by 0.4889 and get a result of 1.4667.

• 5

  Divide the result from Step 4 by the maturation correction to calculate the reticulocyte production index. In the example, you would divide 1.4667 by 2 and get a result of 0.73335.