Nancy Kovacs posted this message on the Medlab-L list and has given me permission to post it here.
Hello! I am a member of the MedLab Listserve and have often seen your postings about coagulation issues. Perhaps you can help us with our PFA-100 questions. We have a pain management clinic and wanted to cease doing bleeding times that were requested before invasive procedures such as epidural injections. We are just about ready to bring our PFA-100 analyzer into service – but – we read in the literature that this test is not to be used as an indicator of propensity for surgical bleeding and is not
sensitive to Plavix. Apparently it is to be used to monitor aspirin and DDAVP therapy. So – our question is – are we back to bleeding times for our pain clinic ? Or should we just advise the doctors of the limitations of the test? If you are doing this test at your institution – what clinical utility does it have for your physicians? Any information, guidance or references you could give us would be greatly appreciated. Nancy
Nancy Kovacs MT(ASCP)
St. Charles Mercy Lab
Oregon, Ohio 43616
Thank you for your question, Nancy, and for permission to post it.
If you can convince your physicians and surgeons of this, screening for a bleeding tendency prior to a procedure has no predictive value, no matter whether you use the bleeding time, which has been discredited, the PFA-100, aggregometry or another whole blood method. There were a number of articles recommending against screening in the 1990s, including this review: Munro J, Booth A, Nicholl J. Routine preoperative testing: a systematic review of the evidence. Health Technol Assess. 1997;1(12):i-iv; 1-62. This is a review, and it will direct you to a number of authoritative references. The recommendation against screening even extends to PTs and PTTs, though there is apparent value in a screening platelet count.
If you cannot convince your surgeons to stop acreening, at least you can apply the PFA-100 to aspirin efficacy testing, which is well-validated. It may not be necessary to monitor clopidogrel (Plavix) therapy in addition to aspirin, but if you want to do this, I’d recommend whole blood aggregometry using the inexpensive Choronog WBA aggregometer, or the Accumetrics VerifyNow. Both can monitor for aspirin and clopidogrel, and can be used to satisfy your surgeons’ requirements. There is a nice meta-analysis that supports aspirin monitoring, Snoep JD, Hovens MM, Eikenboom JC, et al. Association of laboratory-defined aspirin resistance with a higher risk of recurrent cardiovascular events: a systematic review and meta-analysis.Arch Intern Med. 2007;167:1593-9.
I’m happy to see several Medlab-L responses that recommend against pre-surgical coagulation screening and provide other authoritative references. I should add that Corgenix Inc. offers a random urine immunoassay for a platelet metabolite, 11-dehydrothromboxane B2 that monitors aspirin efficacy. It is called AspirinWorks and I must disclose I have a minor financial position in the assay. It is offered through Quest and LabCorp.
I hope this has been helpful. Geo.
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