DIC and Shortened PTs and PTTs

This week I am helping to teach CLSC5124, Advanced Hemostasis, for Dr. Elaine Keohane at the University of Medicine and Dentistry of New Jersey. We have five advanced students in the class who are using our  coagulation overview (1 and 2) and our cell-based hemostasis (9 and 10) modules. Yesterday Dr. Keohane passed along this question to Dr. Larry Smith, Director of the Coagulation Laboratories at Memorial Sloan-Kettering Cancer Center and me from one of our students:
“I have seen cases in which the PTs and PTTs went from normal to short. Our lab manager said that this can indicate impending DIC. When the coag times become short it can indicate that the coag cascade has been activated and the patient is in a hypercoagulable state. If the process continues, the coag factors and platelets will be consumed and the PT and PTT times will become progressively longer, along with development of petechiae. Does this sound right to you?”
Hi, Larry and Elaine, it is true that a shortened PT or PTT indicates partial activation of clotting. You can occasionally see this in a tube with partial clotting. However, Larry Smith may have more experience than me in seeing shortened PTs and PTTs early in DIC. It makes some sense, but I have not seen it. I will post Larry’s reply and invite comments from our participants. Geo.