Free
Correspondence  |   March 2001
A Normal aPTT Does Not Guarantee Adequate Coagulation Factor Levels
Author Affiliations & Notes
  • Jun Teruya, M.D., D.Sc.
    *
  • *Northwestern Memorial Hospital, Chicago, Illinois. j-teruya@northwestern.edu
Article Information
Correspondence
Correspondence   |   March 2001
A Normal aPTT Does Not Guarantee Adequate Coagulation Factor Levels
Anesthesiology 3 2001, Vol.94, 542. doi:
Anesthesiology 3 2001, Vol.94, 542. doi:
To the Editor:—
Spahn and Casutt 1 reviewed the strategies of how to reduce allogeneic erythrocyte transfusions. They briefly discussed the importance of transfusion algorithms based on coagulation monitoring. We would like to mention that a single coagulation factor deficiency may not be detected by routine coagulation assays. Recently, we observed a patient with an F11  deficiency who bled more than expected during surgery. Results of routine presurgical tests, which include prothrombin time, activated partial thromboplastin time (aPTT), fibrinogen, and platelet count, were normal. F11  was later found to be low at 11%.
Although hemostasis is complex in vivo  and laboratory testing does not always predict intraoperative bleeding, prothrombin time, aPTT, and fibrinogen data usually are ordered preoperatively. When prothrombin time and aPTT are within the normal range, it is assumed that each coagulation factor concentration is adequate for surgery (i.e.  , 30% of plasma factor concentration). 2 However, factor sensitivity for aPTT depends on the coagulation factor, the aPTT reagent, and the instrument. Our normal range for aPTT is 25.0–35.0 s, verified by analyzing 15 healthy men and 15 healthy women (mean ± 2 SD). Table 1shows the factor sensitivity for intrinsic factors using Synthasil®(Lexington, MA) performed on the CS6000 coagulation analyzer (Sysmex, Long Grove, IL). Even when F8  and F11  concentrations are 30%, aPTT was normal. Especially for F12  , in which congenital deficiency is not uncommon, aPTT was normal when the concentration was down to 9%.
Table 1. Effects of Intrinsic Coagulation Factor Deficiencies on aPTT Results
Image not available
Table 1. Effects of Intrinsic Coagulation Factor Deficiencies on aPTT Results
×
Therefore, it should be emphasized that obtaining bleeding history, especially after surgery or tooth extraction, is important to suspect a bleeding diathesis. Clinicians should be aware of the factor sensitivity of the current aPTT in their hospital when considering plasma transfusion.
References
Spahn DR, Casutt M: Eliminating blood transfusions: New aspects and perspectives. A nesthesiology 2000; 93: 242–55Spahn, DR Casutt, M
American Society of Anesthesiologists Task Force on Blood Component Therapy: A report by the American Society of Anesthesiologists Task Force on Blood Component Therapy: Practice guidelines for blood component therapy. A nesthesiology 1996; 84: 498–501American Society of Anesthesiologists Task Force on Blood Component Therapy:,
Table 1. Effects of Intrinsic Coagulation Factor Deficiencies on aPTT Results
Image not available
Table 1. Effects of Intrinsic Coagulation Factor Deficiencies on aPTT Results
×