The correct order of filling blood collection tubes is crucial to prevent sample contamination and alteration of test results.
Whether using a tube holder or a syringe, the filling order remains the same.
Recommended Filling Order
Blood Culture Tubes or Vials (Sterile)
Light Blue Stopper Tubes (Sodium Citrate)
Serum Tubes (with or without clot activator or gel separator)
Green Stopper Tubes (Heparin)
Lavender Stopper Tubes (EDTA)
Gray Stopper Tubes (Glycolysis Inhibitor)
Additional Notes
Some facilities may modify this order based on internal studies and variables unique to their system; therefore, follow your facility's established protocol.
Contamination Risk and Impact on Test Results
Additive Carryover: Puncturing a tube stopper can transfer additives from one tube to the next; even minute amounts can drastically alter test results.
Importance of Order: Following the prescribed order of draw doesn't prevent additive carryover, but it minimizes its impact due to the nature of the tests performed on each tube type.
Example of Negative Impact of Incorrect Order
EDTA Tubes:
EDTA is naturally high in potassium.
If used out of order, it can affect potassium test results.
Example: A patient with low potassium might receive a falsely normal result if the order isn't followed, which can be dangerous, especially if the patient is being cleared for surgery.
Conclusion
Adhering to the correct order of filling blood collection tubes is essential to ensure the accuracy and reliability of blood tests.
Always follow your facility's established protocol to avoid problems caused by additive contamination.