A patient’s peripheral blood film shows agglutinated RBCs, and the CBC indicates an elevated MCHC. How will other parameters be affected?

The situation described indicates agglutination of red blood cells (RBCs) alongside an elevated mean corpuscular hemoglobin concentration (MCHC). When RBCs are agglutinated, they tend to form clusters, which leads to an erroneous or inflated calculation of cell volume.

In a sample with agglutinated cells, the mean corpuscular volume (MCV) will often appear increased because the automated hematology analyzers measure the aggregated cells as larger entities than they actually are when dispersed. Thus, the calculated MCV is higher than it would be if the cells were not agglutinated.

However, the RBC count typically appears decreased in the presence of agglutination. The counting algorithms in analyzers can misinterpret aggregates of cells as fewer, individual cells, leading to an underestimation of the total RBC count. Therefore, with the MCV increased and the RBC count decreased, the parameters align with what is demonstrated in choice C. This relation of increased MCV with a decreased RBC count contributes directly to the aforementioned elevated MCHC, as the concentration of hemoglobin rises relative to the number of RBCs present.