Erythrocyte sedimentation rate in glass and plastic pipettes

In the blood collection practice there is a growing number of different closed systems. They often use plastic pipettes for testing the erythrocyte sedimentation rate (ESR) according to Westergren. Our previous experience with plastic pipettes as a part of the system Venoject II suggested that slightly higher values were obtained when compared to glass pipettes. In order to confirm these findings a special comparative trial was performed in a group of 302 blood samples. Statistical evaluation proved a significantly higher sedimentation rate in plastic pipettes. Based on the values from another group of 132 healthy adults we try to draw conclusions on the reference interval of ESR in plastic pipettes. We confirmed that no additional information can be derived from ESR values after two hours.