Comparison between siliconized evacuated glass and plastic blood collection tubes for prothrombin time and activated partial thromboplastin time assay in normal patients, patients on oral anticoagulant therapy and patients with unfractioned heparin therapy.

INTRODUCTION

The study was designed to evaluate whether there was a statistically significant effect between evacuated glass tubes and plastic tubes on prothrombin time (PT) and activated partial thromboplastin time (aPTT).

METHODS

Blood samples were drawn into four different tubes from three patient populations-apparently healthy patients, patients on oral anticoagulant therapy with vitamin K antagonists (OAT-vka) and patients being treated with unfractioned heparin (UFH). Testing was performed on an automated coagulation analyzer, and statistical analysis was achieved using a test of variance (anova).

RESULTS

For normal patients, there were no statistically significant differences for the aPTT test; however, there were statistically significant differences for the PT test. For patients on OAT-vka, statistically significant differences were clearly observed between the four tube types for the PT test. For patients treated with UFH, there were no statistically significant differences for the aPTT test.

CONCLUSION

The data showed a statistically significant difference between glass and plastic tubes in the normal population only for the PT test, with consequent repercussions for patients on OAT. This means that appropriate care and validation should take place whenever there is a change in tube type.