Lupus Anticoagulant

Mixing Study: LA Effect?

Hello Mr. Fritsma! My name is Agustin Rodriguez and I am a haematologist from Spain. I have a question for you, if you are so kind to ansxwer it: I have a patient with a lupus anticoagulant. His PTT (aPTT) is 46 s; normal aPTT is 30 s in my laboratory. The inmediate mixing study 1:1 with […]

Lupus Anticoagulant

Hex-phase Only for LA?

From Lorna Bogertman, Valley Health: Hello George, I have a question concerning lupus anticoagulant (LA) testing. We have had several requests from physicians to perform hexagonal phase LA testing only. Is it valid to perform this test without the rest of the LA profile? We have found that if we performed Stago’s LA-sensitive partial thromboplastin time […]

Lupus Anticoagulant

STAT Lupus Testing?

From Ben Troyer at Med Central Health System: Should lupus anticoagulant testing be offered on a STAT basis? Our LA test volume is pretty low—we average 3–5 requests per week. We make the test available as a STAT, but I’m not sure that this is necessary or appropriate. I’d appreciate any input. Thanks! Hi, Ben, great question. At our institution we […]

Lupus Anticoagulant

In Vitro LA Mechanism

From Kathy Doig, PhD, Michigan State University (Go Spartans!). George – what is the current thinking on how LA interferes with our assays? Does the antibody physically block the proteins so they can’t react properly even though they embed in the phospholipids (PLs)? Does it prevent them from embedding in the PLs as they should? Or is it […]

Lupus Anticoagulant

What is an LDT?

From Kelly Townsend, Tri-core Reference Laboratories, Albuquerque. Looking for opinions on what constitutes a “Laboratory Developed Test” in Coag. Obviously if the reagent kit is not FDA-cleared, it will be an LDT, but what about factor assays, etc where there is no real kit. What if you are using a kit with a different calibrator or control […]

DRVVT Reagent Stability

From Dave McGlasson, George, Has anyone got information on storing DRVV screen and confirm reagent aliquots? Can you freeze/thaw them without any loss in activity? That question has come up to me recently.

Lupus Anticoagulant

Revalidating Sta-Clot LA

From Rose Markarian, Supervisor Hematology, Saint John’s Health Center, Santa Monica, CA: Hi George, We perform Stago’s confirmatory hexagonal phase Sta-Clot LA test for lupus inhibitor testing. We validated Stago’s recommended cut off value of ≤ 8.0 seconds several years ago when the test was implemented. Do we have to validate the cut off value with each new lot […]

Lupus Anticoagulant

Factor VIII Inhibitor?

From Deborah Whetzel, Children’s Hospital of the King’s Daughters, Norfolk, VA: We’ve had a couple patients lately that demonstrated inhibition but their factor VIII results are within normal limits or even elevated. The result values differ 30–40% typically between dilutions but as they’re diluted more, the values go up to 300 or 400%. FVIII values that high […]

Bleeding Disorders

Positive DRVVT when Mixing Study Corrects

From Aliaa Amer: Hi George, we are using Actin FSL for our routine activated partial thromboplastin time (APTT, PTT). Whenever we get a prolonged APTT that is >5 s above the upper limit of the norm range we do mixing studies, both immediate and 2 h incubation using 1:1 and 4:1 mix, the latter to detect […]

Lupus Anticoagulant

More on “Unexpected DRVVT Results”

Here is a message about the dilute Russell viper venom time assay (DRVVT) for lupus anticoagulant (LA) from international expert Thomas Exner, HAEMATEX, Sydney, Australia: It was a pleasure to meet you at the International Society on Thrombosis and Haemostasis (ISTH) meeting recently. I would like to respond an interesting question raised on July 16, 2013 in your Fritsma Factor website. […]

Lupus Anticoagulant

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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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