Which color tube is used for the erythrocyte sedimentation rate (ESR) test?

The lavender-topped tube is used for the erythrocyte sedimentation rate (ESR) test because it contains EDTA, an anticoagulant that prevents blood from clotting. This is crucial for the ESR test because the measurement is based on the rate at which red blood cells settle at the bottom of a test tube over a specific period. If the blood were to clot, it would interfere with the test results, making it impossible to accurately measure the sedimentation rate.

In addition to its role in the ESR test, the use of the lavender tube is common for various hematological tests, as it helps preserve the cellular components of the blood sample for accurate analysis.