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A “Wispy” Clot In a Manual PTT

A note from Beth Lewis:

Hi George,

I’ve just signed onto your site and so far am very impressed with its content. I’ll know I’ll refer to it regularly. Thanks so much for setting it up.

 I have a question for which I’ve been unable to find a good answer: When performing a manual test for PTT, due to an error code on our analyzer, if a wispy clot is detected at some point during the testing but does not reach a solid clot by 120 seconds, what would be the best way to report this?

Thanks, Beth

Hi, Beth, thanks for joining and thank you for your question. I’ll put this out there for people to respond, however my approach would be to report greater than 120 seconds (or whatever limit seems appropriate) and append a note describing the clot. It might also be interesting to see how an optical analyzer such as Beckman-Coulter equipment would respond, as these instruments provide a “clot curve.” Geo.

Comments (2)
Kathy Pupek
Sep 11, 2009 9:24am

We do not perform manual tests at our site. This result woul
We do not perform manual tests at our site. This result would be reported as “unable to report due to unstable endpoint” depending on the curve that the Futura/Advance gave. We also run these on an ACL 1000 to see what the clot looks like in the rotor. If you are doing a manual test and you see a clot formed, would that not be the result you would report? I always go back to the old fibrometer that we were trained on and as soon as a fibrin strand was formed, it stopped and that was your PT or APTT result. That’s the advantage of doing manual test verses the automated optical systems. We only report “>” than results if there is no clot evident at all.

Sep 10, 2009 7:36am

We report out any manuals that do not have an end point as &
We report out any manuals that do not have an end point as >225 sec for aPTT’s and > 140 sec for PT‘s. WE have the Beckman Top analyzer and it does produce a clot curve for each sample. We have guidelines in place to determine when a value can be used from the instrument. By analyzing the clot curve, you can determine if a prolonged times is due to low fibrinogen, decreased factors or simply heparin. Each of these have distinctive curve shapes. There are times though that the clot curve cannot be used and a manual is performed. Hope this is helpful.

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