Cutoff Value for Correcting White Blood Cell Count for Nucleated Red Blood Cells: What is it? Why is it Important?

Nucleated red blood cells (RBCs) are normally observed in the peripheral blood of neonates and during pregnancy. Under other conditions, the presence of nucleated RBCs in circulating blood indicates disorder in the blood-producing mechanism. The increased presence of nucleated RBCs, however, falsely elevates the leukocyte count, as measured by most automated hematology analyzers, warranting a manual correction of the leukocyte count. For a long time, cutoff values for correcting white blood cell (WBC) count for the presence of nucleated RBCs have been used regularly, particularly in developing countries. However, because those values are largely subjective, they can vary widely between laboratories worldwide. These varied cutoff values include 1, 5, 10, 20, and 50; it appears that the numbers 5 and 10 are the most common values used in corrections; the reasons require further elucidation. In this article, we discuss the merits of correcting the WBC count for nucleated RBCs at certain cutoff points.