SST Tube Testing Timeline After Collection

Optimal Processing Timeline

The American College of Clinical Chemistry recommends that SST tubes should ideally be tested within 2 hours of collection after proper clotting and centrifugation, though serum can remain stable in the tube for up to 24 hours when refrigerated at 4°C 1, 2
SST tubes require 30 minutes of clotting time at room temperature before centrifugation, with blood sitting upright to allow proper clot formation 1, 2, 3, 4
The entire process from collection to centrifugation should be completed within 2 hours, including the 30-minute clotting time, to prevent biomarker degradation 1, 2, 3
If immediate processing isn't feasible, refrigerate at 4°C for no more than 24 hours to slow down biomarker degradation 1, 3, 4

Centrifuge for 10 minutes at 1500-2000 × g at 4°C to separate serum from the clot and cellular components 3, 4, 6
Serum should be separated from cells and tested within 2 hours of centrifugation to prevent analyte degradation 7
Post-centrifugation delay causes slower but still significant biomarker decline compared to pre-centrifugation delay 1

Refrigeration at 4°C extends stability but should not exceed 24 hours before centrifugation, and after centrifugation and serum separation, samples can be stored at 4°C for up to 4 hours before testing 1, 3, 4, 8, 9
For longer storage, freeze serum at -80°C immediately after separation, and never store serum at -20°C for clinical purposes 7, 9

Temperature management is crucial, as room temperature storage accelerates degradation exponentially compared to refrigeration, particularly for labile analytes 1
Contact time with cells matters, and the 2-hour rule applies to total contact time between serum and cellular components 7
Specific analyte considerations are necessary, as specialized biomarkers, such as Alzheimer's disease markers, are far more sensitive to delays 1, 2