A blood test measuring how quickly red blood cells settle to the bottom of a test tube over one hour. An elevated ESR indicates inflammation somewhere in the body but doesn't specify the location or cause.
From Greek 'erythros' (red) + 'kytos' (cell), combined with Latin 'sedimentum' (settling). First described by Edmund Biernacki in 1897, this test literally measures how fast red cells 'sit down' in a tube.
This 125-year-old test is still used today because inflamed blood is 'stickier' - proteins from inflammation make red blood cells clump together and fall faster, like how wet sand sinks quicker than dry sand! It's one of medicine's oldest 'something's wrong' detectors.
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