Most routine coagulation tests reliable up to eight hours

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

Pierre Toulon, M.D., Ph.D., from the Université Nice Sophia Antipolis in France, and colleagues drew four 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 two centers.

The researchers observed a significant difference in the analytical comparison of aPTT, fibrinogen, FV, and FVIII results after prolonged storage times versus less than two 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 six and eight hours of storage, but only in patients with FVIII >100 IU/dL. The corresponding bias of −5.2 and −8.5 percent, respectively, was within the GEHT (Study Group on Hemostasis and Thrombosis) limits of variation, but evaluation after storage of eight 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 eight hours after blood collection," the authors write. "That optimal delay should be of six hours for FVIII."

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