Phlebotomy Top Gun: Order of Draw - Do We Still Care?

Presenter

Brad Karon, M.D., Ph.D.

• Co-Director of Laboratory Services at Mayo Clinic
• Professor of Laboratory Medicine and Pathology

Introduction

• The session "Phlebotomy Top Gun" focuses on the importance of the order of draw in phlebotomy.
• Case-based presentation format where attendees vote on case scenarios.

Importance of Order of Draw

• Historical question: Why draw serum tube before potassium ethylenediaminetetra-acetic acid (K EDTA) tube?
• Considerations include prevention of contamination:
  1. Contamination by K EDTA can occur if the order is not followed.
  2. Debate about modern equipment's ability to differentiate sources of potassium.

CLSI Guidelines

• CLSI guidelines (GP41) emphasize order of draw:
  • Blood culture → Citrated tubes → Serum tubes → Heparin → EDTA.
• Special precautions to avoid EDTA contamination of serum tubes.

European Federation for Clinical Chemistry Guidelines

• Detailed review of order of draw issues:
  • Hypernatremia, hyperkalemia, hypocalcemia due to incorrect order.
  • Emphasizes importance of order, even in modern settings.

Contamination Mechanisms

• Direct transfer, backflow during closed loop collection, and syringe contamination.
• Studies indicate that contamination is less likely with modern equipment.

Recent Studies

• Studies on 11 healthy volunteers and a larger group of 120 patients showed no contamination in routine outpatient settings using vacutainers.
• Inpatient studies in the UK indicated significant contamination in some cases.

Mayo Clinic Experience

• Uses internal systems to detect contamination; revisits cases with unexpected high potassium levels.
• Evidence suggests contamination often due to syringe draws where order of draw was not followed.

Conclusion

• Order of draw remains critical, particularly with syringe draws.
• Phlebotomy practice should adhere to recommended order to prevent K EDTA contamination.

Phlebotomy Conference Recap

• Emphasizes importance of continued adherence to order of draw guidelines.
• Audience re-polling shows understanding of the importance of the order.

References

• Several studies and papers from European Federation and other sources discussed.