Evaluation of the platelet function analyzer (PFA-100®) vs. the thromboelastogram (TEG) in the parturient

Background: The platelet function analyzer (PFA-100®) is a bedside test of coagulation designed to evaluate platelet function. It measures the time required for whole blood to occlude a membrane impregnated with either epinephrine (EPI) or adenosine 5′diphosphate (ADP). The results are reported as closure time (CT-EPI or CT-ADP) in seconds. The thromboelastogram (TEG) measures whole blood clotting and the maximum amplitude (MA) correlates with platelet count and function. We wished to establish whether there is a correlation between the CT and platelet count, between the CT and MA, and between the MA and platelet count. Methods: Platelet count, CT, and MA were measured in blood drawn from 172 healthy term parturients using the PFA-100®. Results: We were unable to detect a significant correlation between the CT-EPI and platelet count (r = -0.1, P = 0.21), or the CT-ADP and platelet count (r = -0.02, P = 0.83). We also did not find a correlation between the CT-EPI and MA (r = -0.13, P = 0.12) or between the CT-ADP and MA (r = -0.11, P = 0.19). However, we found a significant correlation between platelet count and MA (r = 0.33, P < 0.001). Conclusions: We conclude that the CT does not correlate with the platelet count or MA in the parturient, but the TEG does. Therefore the TEG may be a better tool to evaluate coagulation in the parturient with thrombocytopenia.