The time period between collection and centrifugation of a blood sample can be a variable affecting the accuracy of patient test results.
Manufacturers of evacuated collection tube systems will recommend a specific period of time to allow blood to clot in the tube prior to centrifugation. This may range from 20-30 minutes depending on the manufacturer. Some clot activators are coated onto the interior surface of the tube and may reduce the required wait time to 5-10 minutes. Failure to adhere to these wait periods may result in fibrin clots forming within the serum phase of the centrifuged sample. Additional handling may be needed to remove these clots before automated or manual sampling can occur.
On the other extreme, waiting too long between collection and centrifugation provides the environment for ongoing metabolic processes of the viable blood cells within the collection tube. This may result in decreased blood glucose levels and the tendency of components from within the blood cells to leach into the serum. Glucose in whole blood is known to decrease by 7-10% per hour.
