I [Geo] received this question on 4-6-21 from Don Wahl, Core Laboratory Manager, Sanford USD Medical Center, Sioux Falls, SD. “Why do coagulation tests need to be quick- thawed at 37°C? If samples are thawed at room temperature what would be the effect on the coagulation testing?”
Hello, Don, and thank you for your question. A five-minute thaw at 37°C is recommended in CLSI guideline H21-A4, Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays; Approved Guideline–Fifth Edition, 2007, a recommendation that goes back at least to Lenahan J, Smith K. Hemostasis, Edition 14, General Diagnostics, Morris Plains, NJ, 1979. The recommendation reflects concern that prolonged thawing at room temperature is likely to result in the slow loss of thermolabile factors V, VIII, and VWF, and may be accompanied by a rise in pH if the tube is unstoppered. [Harms CS. Coagulation pretesting variables and quality control. In Triplett DA. Laboratory Evaluation of Coagulation. ASCP, 1982.] In addition, maintaining specimens at refrigerator temperatures, 2–4°C activates factor VII in vitro, potentially shortening the prothrombin time. Of course, it is essential that thawed specimens be removed from incubation at the five-minute mark, inverted several times, and tested soon after thawing.
The references I provide use expert consensus for their quick-thaw recommendation. I continue to search for experimental evidence and appeal to our FF participants for support. Although it doesn’t specifically address quick-thawing, I recommend the following article for an otherwise comprehensive approach to coagulation specimen management: Gosselin RC, Honeychurch K, Kang HJ, Dwyre DM. Effects of storage and thawing conditions on coagulation testing. Int J Lab Hem 2015;27:551–9. I hope this helps.