Understanding Serum-Based Blood Collection Tubes: Plain, Serum, and SST Tubes

Plain Tubes (No Additives Tubes), Serum Tubes( Clot Activator Tubes), and SST Tubes (Serum Separator Tubes) are three types of vacuum blood collection tubes that are used to obtain serum specimens for laboratory testing. While they share the common purpose of collecting serum, they differ in design, processing time, and specific applications.

Similarities:

All three tubes are coagulation tubes, meaning they rely on the natural blood clotting process to separate serum from whole blood. Once the blood clots, the tubes are centrifuged to isolate the serum, which is then used for testing. These tubes are primarily used in clinical biochemistry, immunology, and serology tests.

Differences:

Plain Tubes contain no additives with red tube tops ,are primarily used for routine serum biochemistry tests, such as liver and kidney function, electrolyte analysis, and drug level monitoring. are primarily used for routine serum biochemistry tests, such as liver and kidney function, electrolyte analysis, and drug level monitoring. They require longer clotting time (30–60 minutes) and are typically used when absolutely no interference from additives is desired.

Clot Activator Tubes with  red or yellow tube tops are coated with substances that accelerate the clotting process, common applications include glucose, cholesterol, CRP, HIV, thyroid function, and tumor markers. reducing the wait time to around 15–30 minutes. These tubes are widely used for general biochemistry and serological testing.

SST Tubes with yellow or orange tube tops contain both a clot activator and a gel separator. These tubes are widely used for hormone testing (e.g., estrogen, testosterone, insulin), thyroid panels (TSH, FT3, FT4), and tumor marker detection (AFP, PSA, CA-125). After centrifugation, the gel forms a stable barrier between the serum and the blood cells, ensuring better sample stability and facilitating transport. SST tubes are commonly used for hormone tests, thyroid panels, and routine chemistry panels.

Conclusion:

Choosing the appropriate tube depends on the testing requirements and processing conditions. Each of these tubes plays a crucial role in delivering high-quality serum samples for accurate diagnostics.