What does the ESR test measure?

The ESR test, or Erythrocyte Sedimentation Rate test, measures the distance that red blood cells (erythrocytes) settle in a vertical tube over a specified period, typically one hour. This test assesses inflammation in the body; when there are inflammatory processes occurring, the erythrocytes tend to settle more quickly due to the presence of certain proteins such as fibrinogen in the blood. A higher ESR can indicate conditions such as infections, autoimmune diseases, and other inflammatory disorders.

While options discussing glucose levels, oxygen rates, or abnormal cell presence might seem relevant to blood testing, they pertain to different tests. Glucose levels are assessed through a glucose test, the rate of oxygen is typically evaluated with an arterial blood gas test, and abnormal cells are commonly identified through cytology or biopsy. Thus, the specific function of the ESR test is solely focused on measuring the sedimentation rate of erythrocytes, making the correct answer the measurement of the distance erythrocytes settle over time.