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

Choice A reason:
Collecting the specimen in an SST (serum separator tube) is not suitable for ABG (arterial blood gas) analysis. SST tubes are used for chemistry tests that require serum separation after centrifugation and are not designed for the preservation of blood gases.

Choice B reason:
Placing the specimen in ice is the correct action when transporting a specimen for ABG analysis. Cooling the specimen slows down metabolic processes, which can alter the levels of gases and pH in the blood if not promptly analyzed. This is particularly important if there is a delay expected in the analysis of the ABG specimen.

Choice C reason:
Collecting the specimen in sodium citrate is not appropriate for ABG analysis. Sodium citrate is an anticoagulant used in coagulation studies and would interfere with the measurement of blood gases and pH levels in an ABG analysis.

Choice D reason:
Inserting the specimen in a light-resistant package is not a standard requirement for ABG specimens. While protecting specimens from light is important for certain types of tests, such as those for bilirubin, it is not necessary for ABG analysis.

Choice A reason:
The order of citrate, heparin, EDTA, and fluoride is not the correct sequence for blood collection. The correct order is essential to prevent cross-contamination of additives between tubes, which could interfere with test results. Citrate tubes should be drawn first to ensure that the blood does not clot prematurely, but heparin should not follow immediately after citrate.

Choice B reason:
Citrate tubes, which contain sodium citrate, are used for coagulation tests and must be drawn first to ensure the proper blood-to-additive ratio. EDTA tubes are drawn next because EDTA binds calcium and prevents clotting, making it ideal for complete blood counts and other hematology studies. Heparin tubes, which prevent clotting by inhibiting thrombin and thromboplastin, are drawn after EDTA. Lastly, fluoride tubes, which contain a glycolysis inhibitor, are drawn to preserve glucose levels and are typically used for glucose and lactate testing.

Choice C reason:
Starting with fluoride is not recommended as it could lead to contamination of the EDTA and heparin tubes with fluoride, which could affect the results of certain tests, such as calcium determinations in heparin tubes. The order of draw is designed to minimize such risks.

Choice D reason:
This sequence is incorrect because fluoride tubes are not drawn before EDTA and heparin tubes. The presence of fluoride could potentially contaminate the subsequent tubes and alter the results of the tests that require heparin or EDTA as an anticoagulant.

In phlebotomy, following the correct order of draw is crucial. The order is established based on the type of additive in each tube and its potential to interfere with tests conducted in subsequent tubes. The standard order is: blood cultures, citrate tubes, serum tubes with or without clot activator and gel, heparin tubes with or without gel, EDTA tubes, and lastly, fluoride tubes. This sequence helps prevent cross-contamination and ensures the accuracy of laboratory results, which are critical for patient diagnosis and treatment.