Reticulocyte production index
The reticulocyte production index (abbreviation: RPI ) is a key figure that shows the regenerative capacity of erythropoiesis . It is determined using the following formula :
background
In principle, the percentage of reticulocytes in the peripheral blood is a suitable marker for assessing the activity of the formation of new red blood cells in the bone marrow . The reticulocyte production index corrects this value by two factors and thus leads to more meaningful values, especially when assessing anemia .
Reticulocyte shift
The reticulocyte shift describes the shift in the maturation site of the reticulocytes from the bone marrow into the blood depending on the hematocrit . A sharp drop in the hematocrit leads to an earlier exit of the reticulocytes from the bone marrow and to a correspondingly longer retention time of the erythrocyte precursors in the peripheral blood.
Such a shift in the place of maturation leads to an increased proportion of reticulocytes in the blood with the same reticulocyte production. The informative value of the reticulocyte fraction as a key figure for the activity of erythropoiesis is therefore limited in this case. For this reason, the reticulocyte production index corrects the proportion of reticulocytes in the blood by the reticulocyte shift in days (= days that a reticulocyte spends in the peripheral blood ). The shift assumes the following values depending on the hematocrit:
| Hematocrit | Reticulocyte shift in days |
|---|---|
| 45% | 1 |
| 35% | 1.5 |
| 25% | 2 |
| 15% | 2.5 |
Hematocrit
Furthermore, the reticulocyte production index normalizes the relative proportion of reticulocytes in the blood to a uniform hematocrit of 45%. This increases the comparability of the key figure with different levels of cellular components in the blood. With the same absolute reticulocyte count cp, a low hematocrit leads to increased relative proportions of these erythrocyte precursors in the blood. This in turn limits the informative value of the relative reticulocyte count as a marker for the regenerative capacity of the erythropoietic system.
Physiological values and pathologies
In healthy, non-anemic people, the reticulocyte production index increases around 1. In the case of anemia RPI allows differentiation between anemia in undisturbed erythropoiesis (RPI> 3) and anemic syndromes with relative erythropoietic insufficiency (RPI <2).
literature
- ↑ G. Herold: Internal Medicine . Herold, Cologne 2012, ISBN 978-3981466010 .