VMAX Error Implies Low Fibrinogen

From Julia Witt, SH (ASCP), Hematology Supervisor, Smith-Glynn-Callaway Clinic, Springfield, MO:

Monday, December 26: We recently had a patient present with an MI. He is on a standard treatment regiment. Upon his arrival at the hospital, baseline coagulation studies were performed. The fibrinogen result exceeds the linearity of the analyzer. A 1:1 dilution utilizing pooled normal plasma yielded a normal fibrinogen result of 130. Clearly this patient has some type of interference, but what could it be?

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Cheat Sheet for Nov-Dec 2011

Our November-December 2011 Cheat Sheet is now online, and will appear in your email inbox just after January 1. Thank you for more wide-ranging questions and concerns. You’ll notice, we’ve not answered all the questions, please look them over, you may have the answer! Geo.

DRVVT Ratio Normalization

In reviewing an article by Dave McGlasson, Wilford Hall USAF Medical Center, San Antonio, that compares several dilute Russell viper venom (DRVVT) kits for their accuracy in detecting lupus anticoagulant, I noticed that Dave advocates for DRVVT ratio normalization, using the attached formula. I may be behind the times, but this is a new concept to me, and it seems to lend greater accuracy to DRVVT reports. Are you using DRVVT ratio normalization? Does it improve your sensitivity and specificity figures?

DRVVT Normalization Ratio

Thanks to a heads-up from Stephen Duff, Co-CEO of Precision BioLogic, please see Zhang L, Whitis JG, Embry MB, Hollensead SC. A simplified algorithm for the laboratory detection of lupus anticoagulants: utilization of two automated integrated tests. Am J Clin Pathol 2005;124:894–901, the original article on this subject.

More on Oral Anticoagulants: Rivaroxaban

Here is a December 19 “FirstWord” post announcing EU clearance of rivaroxaban (Xarelto, Bayer) for stroke prevention and treatment of deep venous thrombosis. Thanks to Steve Duff, Precision BioLogic co-CEO for alerting me to this evidence of the 2011 march to the adoption of new oral anticoagulants.

New Oral Anticoagulants and HIT

An article posted December 15 on TheHeart.org quotes Dr. Jawed Fareed, Loyola University, Chicago, who demonstrated using an in vitro experiment that rivaroxaban, apixaban, and dabigatran do not interact with the anti-platelet factor 4 antibodies responsible for heparin-induced thrombocytopenia with thrombosis, a severe side effect of unfractionated heparin therapy. The findings were reported at this year’s American Society for Hematology annual meeting. Thanks to Dave McGlasson for alerting me to this news.

Heparin Brill-Edwards Curve Calibrators?

Steve Duff, co-CEO of Precision BioLogic received this question from a subscriber:

Has Precision ever considered producing a set of 30 plasmas containing varying levels of unfractionated heparin? I think there is a strong need for a commercial product that can be used to fulfill the CAP requirement for heparin therapeutic range development. It is a struggle for the smaller labs, such as those in community hospitals, to find 30–40 samples that meet the criteria. They may see 2–3 patients a year on unfractionated heparin, but are required to find 30–40 samples from patients on unfractionated therapy, with no concomitant warfarin. These are currently needed during initial installation of an analyzer, and every year when they change lot numbers of PTT reagent, so it would be an ongoing demand.

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PT for Lupus Anticoagulant

From “Sunny,” What is the reason for not using prothrombin time (PT) in investigating lupus anticoagulant (LA)? It is also a phospholipid-dependent assay. Thanks.

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Adapting Ristocetin Cofactor Assay Reagent

Has anyone been able to adapt a third-party reagent for ristocetin onto a Stago STAR-E or Compact? If so, would you be willing to share your experience with the product, validation procedure, etc? Please feel free to reply off-line if you so desire, and thank you in advance,

Dorothy Zdanowicz, Chemistry/Coagulation Supervisor
Englewood Hospital & Medical Center
Englewood, NJ 07631

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