CPT (Certified Phlebotomy Technician) Practice Exam 2026 - Free Certified Phlebotomy Technician Practice Questions and Study Guide

The erythrocyte sedimentation rate (ESR) is a blood test that measures the rate at which red blood cells (RBCs) settle at the bottom of a vertical tube of blood. This process occurs over a specific period, typically one hour. The test is primarily used to assess inflammation in the body; when inflammation is present, certain proteins cause red blood cells to clump together and settle more quickly. Therefore, a higher ESR indicates a greater level of inflammation.

Analyzing how red blood cells separate from blood serum over time gives valuable insights into various conditions, including autoimmune diseases, infections, and some cancers. This makes the measurement of ESR a crucial diagnostic tool in clinical practice. The other options do not pertain to the specific function or measurement provided by the ESR and are unrelated to its purpose in medical diagnostics.