Comparing the prothrombin time INR versus the APTT to evaluate the coagulopathy of acute trauma

In trauma patients, PT/INR or aPTT cutoffs of > or =1.5x normal are often used as triggers for the transfusion of plasma.

To evaluate the ability of the PT/INR or aPTT to predict low coagulation factor levels, these tests were compared to coagulation factor levels in samples with artificially prepared single and multiple factor deficiencies, 9 heparin-contaminated samples, 10 lupus inhibitor-containing samples, 21 samples with elevated factor VIII levels, and 35 samples from acute trauma patients.

The PT/INR and aPTT showed comparable sensitivity for single or multiple factor deficiencies in artificially deficient plasmas, but the PT/INR was more sensitive than the aPTT to low coagulation factor levels in actual trauma patients (sensitivity 84% versus 50%). The aPTT can show false positives with lupus anticoagulants and heparin contamination and false negatives in samples with elevated factor VIII. Thus, in the acute trauma setting, the PT/INR cutoff is a more reliable indicator of reduced coagulation factor levels.