Hoffman and Pennings identified pseudo-reticulocytosis in patients with acute malaria. The reticulocyte count can be used to estimate the percent of erythrocytes infected with the malaria parasite. The authors are from Catharina Hospital in Eindhoven, The Netherlands.
Malaria parasites may cause infected erythrocytes to be counted as reticulocytes because of staining intra-erythrocytic nucleic acid. This can result in a pseudo-reticulocytosis, especially in falciparum malaria when the percent of infected erythrocytes is high.
The reticulocyte count in a patient with malaria will change with the parasite load, while the intrinsic reticulocyte will change much less rapidly.
Using the CELL-DYN 4000 hematology analyzer:
reticulocyte count in percent =
= (0.85 * (percent malaria-infected RBCs)) + 0.81
If this is rearranged:
percent malaria-infected RBCs =
= (1.1765 * (reticulocyte count in percent)) - 0.9529
Limitations:
• An increased reticulocyte count from anemia would cause a falsely elevated estimate for malaria-infected erythrocytes.
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