Integrity of Uncapped Routine Coagulation Specimens Processed in an Automated Integrated Laboratory

Background: The validity of laboratory results depends on pre-analytical variables not detected by conventional quality control. Recommendations are for post-centrifugation coagulation samples to remain capped with cappiercing primary tube analysis. Total laboratory automation integrates analytical platforms with potential incompatibilities necessitating changes including pre-analytical uncapping of samples. Methods: Samples analyzed for Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), D-dimers, Antithrombin and Fibrinogen at baseline, and after 60 and 120 minutes were left at ambient temperature, either re-capped or uncapped, in order to simulate changes from baseline that could occur in uncapped samples on an automation track prior to analysis. Changes were compared to the maximal permissible bias. Results: Sample uncapping for up to 120 minutes at ambient temperature post-centrifugation did not result in clinically significant changes in routine coagulation parameters. Conclusions: Routine coagulation parameters will not change significantly if the primary citrate tubes are uncapped after centrifugation prior to analysis.