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Anti-Xa Nomenclature

FF Participants, the PTT versus Anti-Xa entry has morphed into a discussion of anti-Xa nomenclature, so I’ve decided to start a new thread. Be sure to link back to the prior thread to see where this is coming from.

From Dr. Favaloro: Couldn’t resist adding my support to this. We have moved away from “anti-Xa” ordering, not only due to this previously causing confusion with the ‘factor X’ assay, but also because we now use this method to assess UFH, LMWH, apixaban, rivaroxaban, etc; so, clinicians can no longer order ‘anti-Xa‘ as an electronic order–they have to order the specific drug. If they don’t know what drug is onboard (e.g., emergency admission with abnormal coagulation studies and a suspicion of anticoagulant drug), they can chose ‘unknown anticoagulant drug’ level and we can try to work it out together. We still get paper requests for ‘anti-Xa‘, in which case (should we not be able to clarify the drug with the requesting clinician) the default is our LMWH assay, with this being advised to the clinician in the test report. It takes much effort to change entrenched ordering practice. regards, Emmanuel.

Comments (1)
Anticoagulant Therapy
Sep 16, 2015 3:50pm

From Bob Gosselin:
From Bob Gosselin: Unfortunately our area is also replete with nomenclature that is often confusing to those not in the business (e.g. lupus anticoagulant, ristocetin cofactor versus ristocetin induced platelet aggregation, factor V vs factor V Leiden, etc). I have read so many “layperson” EMR note interpretation of an elevated VWF:RCo being equivalent to VWD:2B because “they” remembered something about ristocetin and something gain in function. At our place, the orderable tests are heparin (must specify UFH, LWMH or pentasaccharide), riva, and apix. However, the written notes are often “anti-Xa” or “factor X” which means the RN or MA has to decipher, and they usually pick the first thing that shows up on the scroll list that comes close to matching. Added comments like “Not the request for heparin assay” or “Not the appropriate test for factor V Leiden” often go unheeded. Here, an isolated factor X request is the trigger to look for meds versus real request (e.g. amyloidosis, warfarin monitoring in high LA patient, etc). It keeps us off the streets…

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