Background: We recently observed that exposure to dry ice lowered sample pH and increased clotting times in lupus anticoagulant analyses, and that such changes could be prevented by placing samples at -80°C after dry ice exposure. In the current study, we sought to evaluate the effects of dry ice exposure on pH and various commonly used coagulation analyses.
Methods: Citrated plasma from 30 healthy blood donors was allocated to four preanalytical regimes: (1) immediate analysis of fresh plasma or (2) storage at -20°C; (3) storage at -20°C followed by dry ice exposure for 24 h or (4) storage at -20°C followed by dry ice exposure for 24 h and storage at -80°C for 24 h before analysis. Analyses of pH, prothrombin time international normalized ratio (PT-INR), activated partial thromboplastin time (APTT), antithrombin, fibrinogen, protein C and protein S was performed.
Results: Samples exposed to dry ice had significantly lower pH, prolonged clotting times in PT-INR, APTT and fibrinogen analyses as well as lower levels of protein C, than samples not exposed to dry ice. These changes in coagulation analyses were not present if samples were stored at -80°C for 24 h after dry ice exposure. Antithrombin and protein S were not significantly affected by dry ice exposure.
Conclusions: Dry ice exposure lowered sample pH and affected various coagulation analyses. These effects were avoided by storing samples at -80°C for 24 h after dry ice exposure.
Keywords: activated partial thromboplastin time (APTT); dry ice; fibrinogen; pH; protein C; prothrombin time international normalized ratio (PT-INR).