Lupus Anticoagulant

Normalized DRVVT Ratio?

George has had several conversations with frequent contributor and international expertDave McGlasson (Wilford Hall USAF Medical Center, San Antonio) about normalizing the DRVVT ratio on the laboratory’s DRVVT mean of the reference interval in accordance withZhang L, et al: A simplified algorithm for the laboratory detection of lupus anticoagulants. Am J Clin Pathol 2005;124:894–901. The author […]

Lupus Anticoagulant

PTT Reagent Selection

For those who participated in our summer, 2011 questionnaire (designed by Precision BioLogic’s marketing analyst Mr. Ankush Randhawa) about the choice of PTT reagent relative to its application and sensitivity to lupus anticoagulant, the results now appear in Fritsma GA, Dembitzer FR, Randhawa A, Marques MB, Van Cott EM, Adcock-Funk D, Peerschke EI. Recommendations for appropriate […]

Anticoagulant Therapy

Error in 2008 IL SCT Procedure

From Laura Paterek: Are you sure the following statement in your article is correct? When a lupus anticoagulant is present, SCT Confirm becomes prolonged beyond the SCT Screen. Normalization renders the SCT insensitive to warfarin. Doesn’t the confirm step decrease when LA is present? Hello, Laura, and thank you for locating this misstatement in my

Lupus Anticoagulant

More on Mixing Studies: Dr. Ortel

We’ve had three posts and several comments regarding lupus anticoagulant (LA) mixing studies since March. These are… March 18, 2012: Test for LA When Mixing Study Corrects? March 22, 2012: Mixing Study Results: Long PT and PTT April 3, 2012: More on LA Mixing Studies In these posts several experts held that it is necessary […]

Lupus Anticoagulant

More on LA Mixing Studies

I received this message from Dr. Rich Cambereri on March 8, and have been holding it pending additional data, but given our March 18, 2012 post from Vanessa Chan in Toronto, and subsequent responses from Herb Crown and Dr. Larry Brace, I’ve decided to use Dr. Cambereri to start a discussion about the use of mixing studies in the lupus anticoagulant (LA) profile: Hi […]

Lupus Anticoagulant

Test for LA When Mixing Study Corrects?

From Vanessa Chan, Sick Kids Hospital, Toronto: Hi George, What is your opinion on the algorithm of tests when testing for lupus anticoagulant? If the mixing tests are normal, should we continue with a confirmatory test? The recent BJH guidelines say, “Mixing tests are a criterion for LA and improve the specificity. However, they introduce a dilution […]

Lupus Anticoagulant

More on Look-Back for Positive APAs

Here is some in depth feedback from “Guest Blogger” Dr. Emmanual Favaloro on the subject of lupus anticoagulant chronicity raised by Pam Owens of TriCore Laboratories, Inc in a Feb 29 post. I sent the highlighted questions to Dr. F on Feb 27: When an LA/APA is defined as “chronic,” does it wax and wane? Not normally according to my understanding, […]

Lupus Anticoagulant

Anti-Xa Assay With LA Present?

Dear George, I have a lupus anticoagulant (LA) positive patient with recurrent pregnancy loss. She is on low molecular weight heparin (LMWH) with a request for an anti-Xa assay. Will LA positive whether it is interference by LMWH? What is your opinion? Hello, Vilas, the chromogenic anti-Xa heparin assay provides an accurate measure of unfractionated […]

Anticoagulant Therapy

Look-back for Positive APAs?

From Pam Owens at TriCore Reference Laboratories in Albuquerque: We are wondering if other labs research their patients’ positive antiphospholipid antibodies (APA) such as the lupus-like inhibitor (LLI, lupus anticoagulant, LA), anti-cardiolipin antibody (ACL) and β-2-glycoprotein 1 (β2GP1)) results to differentiate between persistent and new diagnoses. If so, how far back do they look for a positive? For example, if […]

Lupus Anticoagulant

How Long Do You Wait to do LA Testing?

From someone at Lancaster General: I was wondering whether you could help me with a problem that I have not been able to resolve with certainty. It relates to how long does a patient need to be off warfarin or heparin before lupus anticoagulant testing can be done. I have seen different recommendations ranging from […]

Lupus Anticoagulant

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George Fritsma is a medical laboratory scientist, educator, and author. George holds faculty appointments with Rutgers University and Michigan State University, and is a member of the International Society on Thrombosis and Hemostasis, American Association of Clinical Chemists, and American Society for Clinical Laboratory Science.

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