(HealthDay News) — Most routine coagulation tests can be reliably evaluated after storage at room temperature for up to 8 hours after blood collection, according to a study published in the International Journal of Laboratory Hematology.

Pierre Toulon, MD, PhD, from the Université Nice Sophia Antipolis in France, and colleagues drew 4 evacuated polymer tubes containing 0.109 mol/L tri-Na citrate from 144 patients, including 39 on vitamin K-antagonists. Using the same technical conditions, prothrombin time (PT)/international normalized ratio (INR), activated partial thromboplastin time (aPTT), fibrinogen, factor V (FV), FVIII, and D-dimer were assessed in 2 centers.

The researchers observed a significant difference in the analytical comparison of aPTT, fibrinogen, FV, and FVIII results after prolonged storage times vs less than 2 hours of storage. For all parameters, the mean bias between test results obtained after prolonged storage times remained below the desirable values, except for FVIII assessed after 6 and 8 hours of storage, but only in patients with FVIII >100 IU/dL. The corresponding bias of −5.2% and −8.5%, respectively, was within the GEHT (Study Group on Hemostasis and Thrombosis) limits of variation, but evaluation after storage of 8 hours could result in significant FVIII underestimation.

“These results suggest that, in the studied technical conditions, PT/INR, aPTT, fibrinogen, FV, and D-dimer can be reliably evaluated in tubes stored unspun at room temperature for up to 8 hours after blood collection,” the authors write. “That optimal delay should be of 6 hours for FVIII.”


  1. Toulon P, Metge S, Hangard M, Zwahlen S, Piaulenne S, Besson V. Impact of different storage times at room temperature of unspun citrated blood samples on routine coagulation test results. Results of a bicenter study and review of the literature. Int J Lab Hem. 2017. doi:10.111/ijlh.12660