Abbreviation: RPI
A formula to calculate whether erythrocyte production in response to the degree of anemia is adequate. Calculated as reticulocyte percentage × (patient hematocrit/normal hematocrit)/reticulocyte maturation factor. Maturation factors for a given Hct: 20% = 2.5, 25% = 2, 35% = 1.5, 45% = 1. RPI ≥ 2 indicates adequate erythropoiesis; RPI < 2 indicates inadequate erythropoiesis (hypoproliferation).