Which additive is NOT found in any of the discussed tubes?

Sodium fluoride is known primarily for its role as a preservative in blood collection tubes designed for glucose testing. It prevents glycolysis, ensuring that glucose levels in the sample remain stable for accurate testing. However, while it is used in specific tubes, it is not universally found in all discussed tube types.

The other additives mentioned—sodium heparin, EDTA, and potassium EDTA—have broader usage. Sodium heparin acts as an anticoagulant and is commonly used in blood collection tubes for various tests. EDTA, another well-known anticoagulant, is frequently used in hematology tubes for complete blood counts due to its ability to preserve cell morphology and minimize clotting. Potassium EDTA is also an anticoagulant used in a similar fashion to EDTA but may be included in tubes requiring a specific formulation.

Because of the context and usages of these additives, sodium fluoride stands out as the additive that may not be found in general discussions about blood collection tubes compared to the more commonly used anticoagulants.