Coag tests in DIC

Q. I had some confusion on why the PT, PTT, and TT are prolonged in disseminated intravascular coagulation. Intuitively I thought they might be shorter because everything is already present and turned on due to the constant state of coagulation, but the only way I can think it might be prolonged would be that are the factors being used up which then shows up as a long PT, PTT and TT?  If you could just clarify that for me that would be great.

A. Yes! That’s exactly why they are prolonged! In disseminated intravascular coagulation (DIC) there’s a ton of clotting going on – so the platelets and coag factors are getting used up. As the coag factors get used up, the PT (prothrombin time), PTT (partial thromboplastin time) and TT (thrombin time) go up. You also see increased FDPs (fibrin degradation products) – but that’s an incredibly sensitive test, best used for other purposes.

By the way, Ed’s Pathology Notes has a way to remember the seriousness of DIC – he calls it “Death is Coming.”

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