Anticoagulant Therapy

Establishing PTT Rx Range

From “Kkehoe“: Recognizing that the preferred method for establishing a partial thromboplastin time (PTT) therapeutic range for unfractionated heparin (UFH) is plotting the PTT against the anti-Xa, is there an alternative for labs that don’t perform anti-Xa testing? Are you aware of any commercial kits that can be purchased and used? We currently purchase a […]

Anticoagulant Therapy

Monitoring Heparin with the Anti-Xa assay

From Crystal Azavedo: Hi George, Are you aware of any observation or randomized controlled trial data that compares bleeding and thrombosis risk in patients receiving unfractionated heparin monitored with the activated partial thromboplastin time (aPTT, PTT) compared to monitoring with anti-Xa? In other words, are there clinical outcome data that suggest monitoring with anti-Xa improves patient outcomes? Thanks!! […]

Anticoagulant Therapy

PT Reagents

From Donna Lawler, University of Wisconsin: George, I have been reading with interest the ongoing discussion of PTT reagent selection and enjoyed the corresponding article you cited. I was wondering if you have any similar literature references concerning protime/INR reagents. We use a thromboplastin that has a low ISI (close to 1.0) and good factor sensitivities […]

Anticoagulant Therapy

Case: INR 2.2 but VII and IX are Normal

Here is a puzzler from Pam Owens at Tricore Reference Laboratories in Albuquerque. Hi George, we recently encountered a patient on warfarin (confirmed by clinician) whose international normalized ratio (INR) is 2.22, protein C and S are in the 30–40% range, but her factors VII and IX are “slam” normal. Have you ever encountered this? What could cause it? […]

Anticoagulant Therapy

Antiplatelet Therapy and Cardiac Surgery

A question from my colleague and our former graduate student, Rebecca Jones: Hey, George. When patients are sent to general surgery or to have a stent put in, how much inhibition of platelets is acceptable for procedures to be performed? We have been doing a calculation giving surgeons percent inhibition, but are being asked to switch […]

Anticoagulant Therapy

Panic Value: INR or PT?

Hi, We run coagulation tests at my work place on an ACL 9000 from Instrumentation Laboratory and I would like to know what should be considered as a panic value, a high prothrombin time (PT) value or the international normalized ratio (INR) value? If it is the PT value, what value should be considered as […]

Anticoagulant Therapy

UFH Infusion: a Max Dose

This question was forwarded to me by my friend and colleague, Marisa Marques, MD, Director of the University of Alabama at Birmingham Hospital special coagulation laboratory and transfusion service: “One of our pharmacists asked if there was a maximum dose for the heparin bolus or infusion rate for obese patients since our current recommendations are based on body […]

Anticoagulant Therapy

New Anticoagulants in AF

Guidelines for Coumadin, aspirin, dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis) are changing rapidly, favoring the new oral anticoagulants in most cases of atrial fibrillation. See the current TheHeart.org discussion based on “CardioStim 2012 in Nice, France. Geo

Anticoagulant Therapy

QQ: Anti-Xa Heparin Assay

Here’s a summary of our June, 2012 Quick Question: To perform the chromogenic anti-Xa heparin assay, how many separate reference curves do you maintain for unfractionated (UFH), low molecular weight (LMWH) heparin and fondaparinux? a. One hybrid curve for UFH and LMWH, same curve (computed) for fonda: 7 (16%) b. One hybrid curve for UFH […]

Anticoagulant Therapy

Do You Use Anti-Xa for Heparin?

I received this question from my good friend and colleague, Marisa B. Marques, MD, who directs the transfusion service and special coagulation laboratory at the University of Alabama at Birmingham Hospital: George: Could you find out which medical centers are using anti-Xa instead of PTT to monitor unfractionated heparin? I would like to hear their input and […]

Anticoagulant Therapy

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George Fritsma is a medical laboratory scientist, educator, and author. George is a member of the International Society on Thrombosis and Hemostasis, the International Society for Laboratory Hematology, and the American Society for Clinical Laboratory Science.

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