Certified Emergency Nurse (CEN) Practice Test 2026 - Free CEN Practice Questions and Study Guide

Polycythemia is characterized by an elevated red blood cell count, which can be due to various factors including increased production of red blood cells by the bone marrow or decreased plasma volume leading to a relatively higher concentration of red blood cells in the blood. This condition may be a primary disorder, known as polycythemia vera, or secondary, which can be triggered by conditions that lead to chronic hypoxia such as chronic obstructive pulmonary disease (COPD) or living at high altitude.

In contrast, leukemia involves an increase in white blood cells, which can lead to symptoms such as anemia and thrombocytopenia, while thrombocytopenia specifically refers to a low platelet count. Anemia, on the other hand, is identified by a reduced number of red blood cells, leading to lower hemoglobin levels and decreased oxygen-carrying capacity of the blood. Thus, polycythemia is distinguished by its hallmark symptom of an elevated red blood cell count, setting it apart from the other conditions listed.