On automated hematology analyzers, which one of the following factors will affect both the RBC count and the PLT count?

The correct factor that affects both the red blood cell (RBC) count and the platelet (PLT) count on automated hematology analyzers is the presence of schistocytes. Schistocytes are fragmented red blood cells that can arise in various pathological conditions, such as microangiopathic hemolytic anemias.

When schistocytes are present in a blood sample, they can falsely increase the RBC count, as these fragments are counted as individual red blood cells. Additionally, the presence of schistocytes can also disrupt the normal function of the automated analyzer, leading to potential miscounts or inaccuracies in the platelet count. Their irregular shape and size can interfere with the discriminating abilities of the analyzer's optical or impedance-based methods.

Understanding the effects of schistocytes can enhance the accuracy of hemogram interpretations, as their presence indicates underlying disease processes that could require further investigation or different management strategies.