SR, Sedimentation Rate or Erythrocyte Sedimentation Rate (ESR), is a measurement of how quickly red blood cells in a blood test fall to the bottom of a tube over the course of an hour.
Normal (low) levels of SR suggest that there is little or no systemic inflammation in your body.
Measuring SR is relevant when monitoring inflammatory conditions. Inflammation in the body causes red blood cells to stick together. This, in turn, makes them heavier. When measuring SR, the pace of which the red blood cells fall to the bottom of the tube will determine the level of SR. The faster they fall, the higher the SR.
As a biomarker for inflammation, SR is also used as a tool to diagnose autoimmune conditions including rheumatoid arthritis and lupus erytomatosus.
Low SR levels indicate little or no inflammation in the body. Low levels will usually not have a specific medial significance, however it is sometimes used as a tool to exclude suspicion of certain conditions.
High SR levels indicate that there is an inflammation in the body. However, a high SR is not specific to a particular condition or disease. This means that elevated SR levels can be caused by everything from temporary infections to more chronic autoimmune diseases.
To better understand underlying causes of increased SR levels, the healthcare provider might have to take several factors into consideration such as symptoms, family history and additional tests.