Difficulty: Hard

Average Score: 48%

How can a phlebotomist distinguish whether a collection tube contains serum or plasma?

Rationale

EDTA in the collection tube indicates plasma.

EDTA, or ethylenediaminetetraacetic acid, is an anticoagulant that prevents blood clotting, allowing the collection of plasma when the blood is centrifuged. This property of EDTA makes it a reliable indicator of plasma presence in the tube.

A (SST in the collection tube indicates plasma.) YOUR ANSWER

SST, or serum separator tube, actually contains a gel that separates serum from cells after centrifugation, not plasma. This means that while SSTs are used for serum collection, they do not indicate the presence of plasma, which is collected in tubes containing anticoagulants.

B (Sodium fluoride in the collection tube indicates serum.) YOUR ANSWER

Sodium fluoride is commonly used as a preservative in tubes intended for glucose testing and does not indicate serum. Instead, it is typically found in gray-top tubes, which prevent glycolysis in the blood sample. The presence of sodium fluoride does not relate to serum or plasma identification.

C (Sodium citrate in the collection tube indicates serum.) YOUR ANSWER

Sodium citrate is an anticoagulant used primarily in tubes for coagulation tests, which means it prevents clotting and allows for plasma collection, not serum. Therefore, sodium citrate does not indicate the presence of serum but rather plasma, similar to EDTA.

D (EDTA in the collection tube indicates plasma.) CORRECT

EDTA is an effective anticoagulant that maintains blood in a non-clotted state, resulting in the collection of plasma after centrifugation. Its presence in a collection tube confirms that the sample will yield plasma, making it a reliable marker for distinguishing between serum and plasma.

Conclusion

In phlebotomy, distinguishing between serum and plasma is crucial for accurate laboratory analysis. EDTA’s role as an anticoagulant ensures plasma collection, while other agents like sodium citrate also indicate plasma but not serum. Understanding these distinctions ensures proper sample handling and accurate test results in clinical settings.

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