A white blood cell count and differential that shows an abnormal increase indicates which of the following?

An abnormal increase in white blood cell count is referred to as leukocytosis. This condition typically indicates that the body is responding to some form of stress or infection, such as an inflammatory process, a bacterial or viral infection, or more severe conditions such as leukemia.

Leukocytosis is characterized by an elevation in the overall number of white blood cells, which are crucial components of the immune system. Their increased presence can help indicate an active immune response, as the body mobilizes more white blood cells to fight off pathogens or deal with various stressors.

In contrast, erythrocytosis refers to an increase in red blood cells, neutropenia denotes a decrease in neutrophils (a specific type of white blood cell), and polycythemia generally indicates an overproduction of red blood cells, not white blood cells. Understanding these definitions highlights the specificity of leukocytosis in relation to changes in white blood cell counts, clarifying why this is the correct answer in this context.