Numerous published guidelines encourage appropriate use of fresh frozen plasma (FFP). However, adherence is documented as poor. Therefore, we sought to determine the laboratory effect of FFP administration to patients with an international normalized ratio (INR) less than 1.6 (prothrombin time <1.6 times normal).

We found minimally prolonged INRs decreased with treatment of the underlying disease alone. Adding FFP to the treatment failed to change the decrease in INR over time. In addition, we observed that the change in the INR per unit of FFP transfused can be predicted by the pretransfusion INR (INR change = 0.37 [pretransfusion INR] – 0.47; r2 = 0.82).

With an observed analytic variation of 3.2%, a significant amount of change in the INR following FFP transfusion is expected at an INR of more than 1.7. Indeed, only 50% of patients with an INR of 1.7 showed a significant change in INR with FFP transfusion. Therefore, transfusion for patients not meeting current FFP guidelines does not reliably reduce the INR and exposes patients to unnecessary risk.