How long should a blood sample collected in an SST be allowed to clot?

Allowing a blood sample collected in a serum separator tube (SST) to clot for 30 minutes is appropriate for several reasons. The clotting process is essential for separating serum from the cellular components of blood. In SSTs, the gel barrier assists in the separation after centrifugation.

A clotting time of 30 minutes strikes a balance that helps ensure that the sample has adequately clotted without prolonging the process unnecessarily. If a sample is allowed to clot for less time, the serum may not be sufficiently separated from the cells upon centrifugation, which can lead to inaccurate test results. Conversely, allowing the sample to sit too long (beyond 30 minutes) may lead to changes in analyte stability, which can also affect test accuracy.

Other options, while they may seem reasonable, do not align with the standard protocol for SSTs as closely as the 30-minute period. Choices suggesting a shorter or longer duration could compromise the quality of the specimen for testing.