Final answer:
The erythrocyte sedimentation rate (ESR) is a blood test that measures how quickly red blood cells settle out of the watery portion of blood (plasma) over time. It is directly proportional to factors like inflammation and infection, and inversely proportional to factors like red blood cell size and shape.
Step-by-step explanation:
The erythrocyte sedimentation rate (ESR) is a blood test that measures how quickly red blood cells settle out of the watery portion of blood (plasma) over a set period of time. It is reported in millimeters per hour (mm/hr). The ESR is directly proportional to certain factors like inflammation, infection, or autoimmune disorders, which can cause red blood cells to clump together and settle more quickly.
Conversely, it is inversely proportional to factors like the size and shape of red blood cells, as well as the level of plasma proteins that can hinder the settling process.