Usefulness of a New Polymer Sampling Tube for Coagulation Testing in Untreated Patients and in Patients on Traditional Anticoagulant Therapy. Results of a Multicentre Evaluation.

For years, laboratories have used evacuated glass tubes for blood collection. To improve the safety of blood collection, plastic tubes have been developed but various interactions with the coagulation system and/or antithrombotic drugs were reported with the first generation of such tubes. The aim of this multicentre study was to compare the results of different coagulation parameters measured in evacuated polymer (polyethylene terephtalate outer layer and polypropylene inner layer) tubes (Vacuette®, Greiner Bio-One) containing two different citrate concentrations (0.109 M and 0.129 M) with those measured in evacuated siliconized glass tubes (Vacutainer®, Becton-Dickinson) containing the same citrate concentrations. In addition, the impact of aging of the polymer tube was investigated by collecting blood samples in tubes at 11 months (beginning of shelf life=BSL) and at 1 month (end of shelf life=ESF) from expiry (only evaluated using the 0.109 M citrate concentration). A single batch of the different tubes was used in the present study. For that purpose, blood was drawn in the 5 participating centers from untreated patients (n=60), patients on oral anticoagulant treatment (OAT, n=168), and patients treated with either unfractionated heparin (UFH, n=123) or a low molecular weight derivative (LMWH, n=106). The sampling order of the different tubes was randomly defined. Prothrombin time (PT) or INR, activated partial thromboplastin time (APTT), factor V as well as anti-Xa activity (when applicable) were performed in each center using its own routine techniques, immediately after centrifugation. Coagulation activation markers i.e. thrombin-antithrombin complexes (TAT) and prothrombin fragment 1+2 (F1+2) were analyzed in a subset of untreated patients (n=30) after centralization in a single center. In addition, the stability of the samples was evaluated for the routine tests over a 6-hour period in untreated patients. The results of the coagulation tests were significantly different in polymer and glass tubes, from an analytical point of view (paired Student’s T-test). However, the difference was without any clinical relevance (Bland-Altman analysis), whatever the citrate concentration and the patients group. Furthermore, there was no significant difference in the results obtained in BSL and ESL polymer tubes. Interestingly, the plasma levels of TAT and F1+2 were significantly lower when blood was drawn in the polymer tubes for both citrate concentrations, even if the markers remained within the expected range in all cases. A significant evolution of the results, comparable for all types of tubes, was demonstrated for PT, APTT and FV over the 6-hour period. These results suggest that samples collected into the Vacuette® polymer tubes allow accurate routine coagulation testing both in untreated patients and in patients on traditional anticoagulant treatment during the whole shelf life indicated by the manufacturer. In addition, the observation of a lower activation of the coagulation system in the polymer tubes than in the glass tubes, containing a similar citrate concentration, deserves to be further investigated.