Is there any anti-coagulant in my sample tube?

We occasionally get asked if the sample tubes in our kits are missing the anti-coagulant, or if it should be stuck to the bottom and not mixing with the sample.

In fact neither is the case, but we can understand the confusion especially if you have used different kits before.

We use two types of tubes for our tests.

1. Yellow topped SST (serum separator tubes) have a visible gel layer at the bottom, which is used in the laboratory to help isolate the serum (fluid component) from the blood cells and platelets. Most of our blood tests measure serum levels of the biomarkers of interest, so use SST samples for analysis.
2. We also use purple topped (EDTA) tubes. These are used when the blood cells themselves are of interest, for example in a full blood count test. These don't need a separator layer since analysis is done on whole blood to measure cell counts.

Regardless of what tube is included in your kit, both will contain an anti-coagulant to prevent your blood sample clotting.

In both cases the anticoagulant is coated on the tube walls so isn't actually visible!