Which test determines the rate at which red blood cells settle out of the blood?

The erythrocyte sedimentation rate (ESR) test is specifically designed to measure the rate at which red blood cells (erythrocytes) settle to the bottom of a test tube over a specified period, typically one hour. This process involves placing a sample of blood in a vertical tube and observing the distance that the red blood cells fall. The resulting measurement can indicate the presence of inflammation in the body. When inflammation occurs, proteins such as fibrinogen are produced in higher amounts, which can cause red blood cells to clump together and settle more quickly.

In contrast, other tests listed serve different purposes. The hemoglobin test measures the amount of hemoglobin in the blood, which is important for assessing overall oxygen-carrying capacity. The blood glucose test evaluates the level of glucose in the blood, primarily for diagnosing diabetes. A complete blood count is a comprehensive test that provides information on various blood components, including red blood cells, white blood cells, and platelets, but does not specifically measure the sedimentation rate of red blood cells.

Thus, by understanding the particular functions of these tests, it becomes clear that the erythrocyte sedimentation rate (ESR) is the correct choice for determining how quickly red blood