ESR (1h)
What it measures, and what changes the number.
ESR (erythrocyte sedimentation rate) measures how far red blood cells settle in a vertical tube of anticoagulated blood over the first hour. Proteins produced during inflammation make red cells clump and fall faster, so ESR is a general, non-specific marker of inflammation. Spanish language reports may list it as 'VSG 1ª hora'.
It is often ordered with CRP, which responds more quickly to changes in inflammation, and with a complete blood count, because red cell number and shape influence settling.
The sample should be tested within a few hours of collection and kept at room temperature. Anemia, pregnancy, age, sex and blood protein levels all affect the result. The classic Westergren method and automated alternatives are used, and results are reported as distance fallen in millimeters.
Often read alongside: CRP, hs-CRP, White blood cells, Hemoglobin, Red blood cells