Posts - Screening Assays

Oct 15, 2018 5:04pm
Here is another note from Paul Riley, PhD examining the effects of extended half-life factor IX concentrates. on hemophilia B testing. Hemophilia B1:  Therapy Classes and Monitoring
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Oct 15, 2018 12:35pm
I follow-up to our October 6, 2018 post describing emicizumab (HemLibra), I have correspondence dated 9/10/18 from Paul Riley, PhD, MBA, Stago Scientific Business Development Manager for North America. Paul writes, "I was wondering if you should put something on FF about emicizumab, like a survey to find out how people are dealing with it and if they have patients transitioning to that therapy. Here is some information I put together recenly on it in order to give good guidance to our customers when they have questions. There is another approval expected shortly for non-inhibitor patients transitioned over despite there having been several deaths reported recently in patients taking emicizumab." [Added by George, this approval is now in place. also, while it addressed the limitations of the one-stage clotting assay relative to extended half-life factor VIII, the results of our June, 2018 Quick Question, "How do you measure factor VIII?" have a direct bearing on the emicizumab issue]  Paul provides this table for hemophilia A monitoring. Hemophilia A1 Therapy Classes and Monitoring FVIII Inhibitor? Y/N Y/N Y/N Prophylaxis Conventional half-life recombinant or plasma-derived FVIII concentrate Extended half-life recombinant FVIII concentrate Emicizumab Assay for measuring activity OSA or CSA2 OSA3 or CSA using human or bovine materials CSA with human materials or OSA using emicizumab calbrators and controls.4
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Jan 22, 2018 10:41am
From Alan Neal, Pathlab, NZ. Just wanted a private conversation about the January 11, 2018 Fritsma Factor entry, "POC and Plasma-Based PT/INRs." I do not agree with the comments made within this article and challenge the logic used. Essentially, if monitoring an enzymatic pathway such as coagulation, with the 'detector' being used is fibrinogen to fibrin, then that rate of reaction will be dependent on the substrate concentration, i. e., fibrinogen, and the sensitivity of the analyser to detect the end point. So if no or reduced fibrinogen or dysfibrinogen, then reduced Vmax and hence PT/INR will be more prolonged than test system using a clot based end point detection.
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