Final answer:
A cold agglutinin will affect most parameters of the cell counter except for the platelet count, as agglutination primarily involves red blood cells and not platelets.
Correct option is A
Step-by-step explanation:
A cold agglutinin is a type of antibody that can cause agglutination, or clumping, of red blood cells at low temperatures. This can affect various parameters measured by a cell counter. When considering which parameter would likely not be affected by the presence of a cold agglutinin, we can rule out hemoglobin concentration, hematocrit, and red blood cell count, as these can all be impacted by agglutination. The platelet count, however, is the parameter that would typically remain unaffected. Agglutination involves red blood cells binding together, potentially leading to erroneously low counts or altered measurements when these cells are aggregated.
Platelets are not involved in this specific agglutination process, so their count would generally remain accurate in the presence of cold agglutinins.