NHA Phlebotomy Certification Practice Exam

Which component is essential to assess the viscosity of blood?

1. Hemoglobin levels

2. Platelet count

3. White blood cell count

4. Hematocrit

The correct answer is: Hematocrit

The hematocrit is essential for assessing the viscosity of blood as it measures the proportion of blood volume that is occupied by red blood cells. Viscosity refers to the thickness and stickiness of blood, which can affect circulation and how well blood flows through the vessels. A higher hematocrit indicates a greater concentration of red blood cells, which can lead to increased blood viscosity. This is important in diagnosing and monitoring conditions such as polycythemia or dehydration, where the number of red blood cells is elevated. Other components, such as hemoglobin levels, platelet count, and white blood cell count, provide important information about blood function and health but do not directly relate to the measurement of blood viscosity. Hemoglobin levels indicate oxygen-carrying capacity, while platelet count and white blood cell count pertain to clotting and immune response, respectively. Therefore, the hematocrit specifically addresses viscosity by revealing the ratio of cellular elements to plasma in the blood.