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Mixing Studies with Controls

Thanks to all who attended our free webinar, Improving Acute Care with Coagulation Mixing Studies, Wednesday, May 13, sponsored by Precision BioLogic Inc. You can see and hear an archived copy of the entire webinar by registering on the Precision BioLogic web site by June 12. The webinar was hosted by CACMLE.

There was an interesting question at the end of the webinar that requires further discussion,. A participant asked if it was appropriate to use control plasmas as a part of the mixing study. Though it seems appropriate, it is not standard practice to include controls. For those who use controls, what is the nature of your control? Do you use an LA-positive control? A factor-deficient control? Or a plasma that contains a specific inhibitor such as anti-FVIII? Do you perform both an immediate and incubated mix on the control? Thank you in advance for your answer.

Another participant asked about the use of a saline mix, which led us to reprise a 2013 Mixing Study post by Courney Jackson.The 2013 post goes into detail on interpreting the salne mix.



Comments (1)
Mixing Studies
May 18, 2015 12:45pm

Hi George, our protocol has
Hi George, our protocol has controls for both PT and aPTT mixing studies. For the PT mixing study we use a 50:50 mix of absorbed plasma and normal pooled plasma (NPP). For the aPTT mixing study we use a 50:50 mix of Factor VIII deficient plasma and NPP. We have reference ranges established for each component at both immediate and post incubation which is separate and different than a neat PT and aPTT.

You raise an interesting question when you ask if a lupus positive control is mixed with NPP in order to control the lupus anticoagulant component of the aPTT mixing study. We have not considered that, but maybe we should.

As a side note, you have more questions on your site about mixing studies than any other topic. If someone were inclined, they could earn a PhD by developing a standardized protocol for mixing studies. If only I were young……

Herb Crown
St. Louis University Hospital Coagulation Reference Laboratory

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