Final answer:
Blood for an ESR test is typically collected into a tube with an anticoagulant, such as EDTA, and the sedimentation rate is measured without centrifugation to allow natural settling of erythrocytes.
Step-by-step explanation:
The preferred collection method for an erythrocyte sedimentation rate (ESR) test involves drawing a blood sample into a tube that contains an anticoagulant, such as ethylenediaminetetraacetic acid (EDTA) or citrate. Blood samples collected for ESR tests are then evaluated without centrifugation. This is to allow the red blood cells to settle naturally at the bottom of the test tube, which forms part of the test's sedimentation rate measurement. A specialized tube, such as a Westergren tube, is often used for accuracy in measuring the rate at which red blood cells settle.
It is important not to confuse the ESR test with the hematocrit test, although both involve erythrocytes. The hematocrit test requires centrifugation and measures the percentage of red blood cells in the sample, with the resulting separation yielding the buffy coat and plasma layers on top of the erythrocytes.
The sedimentation rate can be affected by various conditions that cause the red blood cells to clump together, leading to faster sedimentation and an increase in the sed rate. This can indicate the presence of certain diseases or inflammatory conditions.