On October 21 I posted my conversation with Steve Duff, co-CEO of Precision BioLogic Inc about establishing the partial thromboplastin time (PTT) therapeutic range for unfractionated standard heparin (UFH) therapy. I speculated that with the arrival of all the new anticoagulants, the ex vivo Brill-Edwards curve is becoming a thing of the past. Steve challenged my statement, prompting me to reprise a Quick Question:
“How do you produce your PTT therapeutic range for monitoring UFH?”
a. Prepare a Brill-Edwards ex vivo curve using anti-Xa as the reference method: 54 respondents, 57%
b. We bypass the PTT and use the anti-Xa for heparin monitoring: 25 respondents, 26%
c. Spike a normal plasma with measured UFH and perform PTTs: 15 respondents, 16%
d. UFH has been largely replaced, we do little UFH monitoring: 1 respondent, 1%
With these results in plain sight, I have to throw in the sponge! I may defend myself by saying, at least a significant minority have moved to the chromogenic anti-Xa assay, which is less prone to interference than the PTT, but I’m forced to acknowledge that over half of us continue to prepare the Brill-Edwards ex vivo curve.
I should mention to those who are spiking normal plasma with heparin that this method, owning to poor linearity at the high end, is not recommended by the laboratory accrediting agencies and probably should be abandoned. For those participants, it may be productive to go right to the chromogenic anti-Xa assay and bypass the PTT altogether. Meanwhile, watch for a new Quick Question on Monday. Geo.