Which test is increased in acute infections?

The correct choice is related to the reticulocyte count. In acute infections, the body's immune response is triggered, which often leads to an increased demand for red blood cells due to hemolysis or blood loss caused by the infection. The bone marrow responds to this demand by releasing more reticulocytes, which are immature red blood cells. Therefore, the reticulocyte count is increased in acute infections as the body attempts to regenerate red blood cells more rapidly.

In contrast, osmotic fragility tests assess the susceptibility of red blood cells to hemolysis when placed in hypotonic solutions, which is not directly altered during acute infections. Blood cultures are used to detect the presence of pathogens in the bloodstream, but they do not provide a direct measurement that increases specifically as a response to the infection itself. Hematocrit levels can vary depending on hydration status and other factors but do not necessarily increase solely due to the presence of an acute infection.