Which of the following lab values indicates a crisis in a patient's hematology measures?

A white blood cell (WBC) count below 4,000/uL indicates leukopenia, which signifies a reduced number of white blood cells in the circulation. This condition can critically compromise a patient's immune response, increasing their vulnerability to infections and indicating an underlying hematological issue. Such a low WBC count is often indicative of a significant crisis, particularly in patients undergoing treatments like chemotherapy or those with certain bone marrow disorders, as these situations can lead to a drastic reduction in WBC production.

In contrast, a hemoglobin level above 14 g/dL, a platelet count of 300,000/uL, and a hematocrit of 45% generally indicate normal or acceptable hematological statuses. These values suggest adequate oxygen-carrying capacity and platelet levels, neither of which pose immediate concerns or crises in hematology. Therefore, the marked deficiency noted in the WBC count clearly signifies a hematological crisis, warranting immediate clinical attention.