here is a message from Jennifer at the University of Tennessee at Memphis, who is doing a research study about utilization of the INR. Jennifer would like to document the frequency of PT tests ordered daily, nationwide. Please send a reply giving your laboratory's volume so she can extrapolate to estimate a nationwide volume. Thank you.

Jennifer: thanks to Stephen Duff at Precision Biologic, we've located a CDC report on laboratory testing volumes. Click on http://wwwn.cdc.gov/mlp/coagulation_resources.aspx, it should bring you there.

We've posted a new quick question sent by Kim Kinney of Clarian Laboratories in Indianapolis. I look forward to seeing your answers, and encourage you to submit quick questions for a survey also.

Here is a question from Joseph A. De Vito

In reading an article, Quote: The INR is a standardized number and is calculated from the patient PR, the normal range for PT, and the sensitivity of the reagent used.   Please explain to me the following:
(1) The patient PR
(2) Normal range for PT
(3) Reagent used
I will await your reply. Thanking you. I remain, respectfully, Joseph A. De Vito

I've had several discussions with Marisa Marques, MD, my friend and colleague in Laboratory Medicine at the University of Alabama at Birmingham about "warfarin resistance," as she was managing two deep vein thrombosis patients, one of whom required warfarin at 25 mg/day and one at 35 mg/day. We were looking for a polymorphism associated with a need for increase warfarin dosage, but could find none. I confirmed this by phone with Elaine Lyon, PhD, Scientific Director at ARUP in November. However..

On October 30, 2007, under the title, “Anticoagulant Forum and CYP2C9,” Kim Kinney and I briefly addressed the polymorphisms that affect warfarin dosage. In August, 2007 the FDA had begun requiring a box on the warfarin label recommending genetic screening prior to dosing as a patient safety measure. Here is a little more detail...

Presenter: Dorothy Adcock-Funk, MD
Panelists: Kandice Kottke-Marchant, MD, PhD; Marisa B. Marques, MD; John D. Olson, MD, PhD
Moderator: George A. Fritsma, MS MT (ASCP)

Precision BioLogic Laboratory Medicine Roundtable, June 20 and 21, 2008, Dartmouth, Nova Scotia

In addition to Wendy Porteous, Steve Duff and Michael Scott, I would like to acknowledge Dean Willett, Sandy Morrison, and all the Precision BioLogic Inc. folks who participated in our round-table discussion.

We have employed the time-honored partial thromboplastin time assay (PTT, activated partial thromboplastin time, APTT) to monitor unfractionated heparin (UFH) and the intravenous direct thrombin inhibitors (DTIs) Argatroban (Novostan®), Lepirudin (Refludan®) and Bivalirudin (Angiomax®). Though we have developed and published therapeutic target ranges, the PTT suffers from several interferences. It is prolonged by parallel warfarin therapy, lupus anticoagulant, and congenital or acquired factor deficiency. In these circumstances the PTT anticoagulant response is exaggerated and unreliable. Conversely, elevated factor VIII and fibrinogen shorten the PTT and underestimate anticoagulant effect, a circumstance called in vitro drug resistance. The PTT does not lend itself to inter-laboratory normalization, as a variety of reagent and instrument combinations generate diverse anticoagulant responses.

Here's an interesting question from Anita D'Antonio.

Several of our hospitals Hematologists/Oncologists have concerns with the sensitivity of the reagent we use for Prothrombin testing. The reagent is Diagnostica Stago STA-Neoplastine Cl Plus with a 1.32 ISI. They believe the reagent is too sensitive and is generating needless consults and follow-up testing on patients who do not have a bleeding disorder. I believe the more sensitive assay is best. How can I present this information to the medical staff?

Anita D'Antonio

Click "Full Story" below to read David McGlasson's response.

Here is an interesting question from Dr. Michael D. Blechner of the University of Kentucky:

First I would like to compliment you on a great web site; an extremely valuable resource for myself as well as our residents. Second, I would love for you to do a followup “Quick Question” to evaluate how folks are reporting out and interpreting heparin dependent antibody test results. We use the GTI assay and stick with their recommended cutoff, OD >0.400. As you may know this assay has a confirmatory step after the addition of heparin. We report out positive, negative or equivocal (OD > 0.400 but not confirmed with heparin). We do not report out the ODs. I would be very interested to know who is reporting out the ODs and if folks have added any interpretive categories and/or interpretive comments; for instance, weak positive versus strong positive. The GTI cutoff of 0.400 makes for a pretty sensitive assay. It’s the resulting poor specificity that plagues us when physicians try to rely too heavily on this assay for diagnosis of HIT. Thanks.

Mike Blechner

Michael D. Blechner, MD
Assistant Professor, Pathology & Laboratory Medicine
Director, Pathology Informatics
Director, Coagulation Laboratory
University of Kentucky Medical Center
Lexington, KY

Dr. Marisa B. Marques, director of the University of Alabama at Birmingham Hospital Special Coagulation Laboratory reports the American College of Chest Physicians Eighth ACCP Conference on Antithrombotic and Thrombolytic Therapy has released "Antithrombotic and Thrombolytic Therapy: 8th Edition Guidelines." The guidelines are available free online to non-subscribers at Chest 2008:133 (6 suppl) . This replaces the 7th Conference Guidelines published in September of 2004.

From Cynthia McKenzie, RN:

Many years ago I knew of a patient who was stable on Coumadin. A PT/INR was drawn on a Thursday and it was therapeutic. On Friday evening she complained of nausea and requested cranberry juice. A 1/2 to 1 gallon container was brought in by a family member. She refused food and drank only water, Seven-up and cranberry juice all weekend. I returned Monday and was called to her room. The AM nurse found her unresponsive with her gaze upward and to the left. I called her MD and had her transported for a stat CT. Her INR was 15. She had a HUGE IC bleed, incompatible with life and died shortly after.
 
There is pitifully little information related to cranberries and Coumadin. Nursing home personnel often suggest cranberry tablets to physicians for UTI prevention. Dieticians may place cranberry juice on the menus without knowing who should not have it.

 
MORE articles for MD and NURSING journals and DIETICIANs PLEASE!
 
Cindy, RN

Thank you for this case history, Cindy. I hope a lot of patient care personnel read it. Geo.