Case Studies: Case Study 8

Discussion

  • When drawing blood into evacuated tubes, it is best to draw the tiger top and red top tubes first, so that tissue fluids and fragments that cause blood to clot are retained in a tube which will clot anyway. Such tissue fluids and fragments are most likely to be present in the first tube to be drawn. If tissue fluids and fragments are present in a light blue top tube used for coagulation tests, they will interfere with the test results. However, recent studies have shown that accurate coagulation results may be obtained from the first tube drawn. It is nevertheless recommended that tiger and red top tubes be drawn first when using the evacuated tube system.
  • If blood had been drawn first into a syringe, the order in which the blood is expelled from the syringe into the tubes would be different. Since no anticoagulant is present in the syringe the blood must first be expelled into the light blue top tube, then the lavender top tube, and finally the tiger top tube. This is so that the blood is promptly mixed with the anticoagulants present within the light blue and lavender top tubes before clotting begins. Clots in a lavender top tube are likely to cause a falsely low platelet count.
  • Relevant topics:
  • Lavender top tubes, Light blue top tubes

Get online OSHA safety and compliance training for your clinical laboratory employees.

Phlebotomy course details »

Learn more about laboratory continuing education for ASCP, AMT, NCA, and state renewal and recertification requirements »

Get information on laboratory safety and compliance courses for clinical and medical laboratories »