I’ve received four expert follow-up comments to our July 5 D-dimer Efficacy in Factor V Leiden Mutation post. Here they are, in order of receipt:
From Dr Emmanuel J Favaloro, Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, NSW Australia:
Hi George, I have no idea about FVL influencing D-dimer development; I would suspect it feasible that it would slow the development, but eventually a positive D-dimer would eventuate, and in the time course of development, a DVT should show up as a positive D-dimer in FVL positive patients to a similar level as that in FVL negative patients. I suspect it would be very difficult to show a statistical difference in D-dimer levels post DVT/PE/etc in FVL positive vs negative patients – the number of patients required would be far too large.
From Dave McGlasson, 59th Clinical Research Division, Wilford Hall USAF Medical Center, Lackland AFB, TX:
One of the issues I could see as a problem with the D-dimer comparison is the issue of age and what is considered normal with different age groups and whether normal specimens are collected on in-patient populations and out-patient subjects.
From Dorothy M. (Adcock) Funk, M.D., Medical/Laboratory Director, Esoterix Coagulation, Englewood, CO:
George, I wonder if the clot burden in a superficial thrombophlebitis is sufficient to always cause the D-dimer to elevate above a given cut off. I think not. This of course also depends on the age of the clot compared to when testing was performed. Further, D-dimer is not FDA approved to exclude superficial thrombosis. Dot
From John Olson, MD, Director of Clinical Laboratories, University of Texas Health Science Center, San Antonio, TX:
I don’t have anything to add to Dot’s comments. I do think that a problem with superficial phlebitis is the age of the clots. Production of D-dimer from fresh clots falls of after about 2 weeks so the duration of the thrombi is also a consideration. Whether superficial phlebitis will elevate the dimer is a function of the amount of fresh clot there is to lyse, thus I expect the dimer response would be variable. Thanks, John
Thanks to everyone for responding, and I hope this is helpful to our original questioner. I’d been making the assumption that a superficial thrombophlebitis would consistently generate a positive D-dimer, however it appears the effect. if present, may be short-lived.