Lupus Anticoagulant

August 2022 Quick Question: LAC Testing Responses

Our August 2022 Quick Question attracted 34 responses [despite our discouraging “Recaptcha” security function] and asked, “You test for lupus anticoagulant [LAC] using a low-PL PTT reagent and a hex-phase high-PL mix. The mix results are 10 seconds shorter than the first test. What do you conclude?” LAC positive 32% [11] LAC negative 18% [6] […]

Lupus Anticoagulant

August 2022 Quick Question: LAC Testing

Our August 2022 Quick Question addresses lupus anticoagulant testing, a member of the standard thrombophilia screening profile. “You test for lupus anticoagulant [LAC] using a low-PL PTT reagent and a hex-phase high-PL mix. The mix results are 10 seconds shorter than the first test. What do you conclude?” The question illustrates the PTT-based LAC test […]

Lupus Anticoagulant

Covid and Lupus Anticoagulant

Two compelling publications appear to implicate lupus anticoagulant as a key factor in prolonged PTT results documented in seriously ill Covid victims. These could account for prolonged PTTs in the absence of hemorrhage. They are: Bowles L, Platton S, Yartey N, et al. Lupus anticoagulant and abnormal coagulation tests in patients with Covid-19. Downloaded from […]

Lupus Anticoagulant Testing

Maureen (Mo) Tacke, St. Luke’s Health System, sent this case. A woman who had experienced one normal fetus loss at longer than 10 weeks’ gestation and one unexplained spontaneous miscarriage at shorter than 10 weeks’ gestation but no additional thrombotic episodes had the following results: Initial: DRVVT ratio: 1.70 (limit 1.20); silica clot time ratio […]

Lupus Anticoagulant

Case: DVT During Pregnancy

Our Quick Question case study for April, 2019, is adapted from Chapter 35 of the March, 2019 6th edition of Rodak’s Hematology, Clinical Principles and Applications: A 33-year-old pregnant woman developed deep vein thrombosis in her left leg. She reported a family history–her mother had an episode of superficial thrombophlebitis and her brother had experienced […]

Lupus Anticoagulant

PTT and C-reactive Protein

From Dean Willett, Precision BioLogic Inc. As I read the 11-8-17 comments from Dr. Elman a bit of a lightbulb went off in my head. I’m sure you’ve seen the various publications that demonstrate the effect of C reactive protein (CRP) on APTT assays. Here are: https://www.ncbi.nlm.nih.gov/pubmed/22224499; and https://biblio.ugent.be/publication/5838447/file/6839536. There have been some proficiency samples […]

Lupus Anticoagulant

LAC Profile: PTT Versus PTT-LA

From “Ari.” Hi George, I stumbled upon your amazing site when researching this question and was wondering if you could shed some light on this. I have a patient who had a DVT. His PCP noted a slightly prolonged aPTT and sent mixing studies. From what I can tell, the aPTT mostly corrected with mix, […]

Lupus Anticoagulant

Is APS Hereditary?

An intriguing case from Heather DeVries, Indiana University Health. Hi George, I have an interesting (cold) case study for you. We recently tested a 44 yo female for lupus antibodies and she had textbook results–nothing equivocal about them. Her history includes a late-term pregnancy loss 12 years ago, and a recent diagnosis of lupus, so […]

Lupus Anticoagulant

ACA Pt Specimens Vs. Calibrators

From Wendy Sutula, Hi, George. We are validating a new vendor’s ACA kit. When we perfom patient ACA tests, the serum samples are frozen at –20 for 2–7 days before tesing. When establishing or validating the reference range for the new vendor’s kit, is it acceptable to use serums which have been collected and frozen […]

Lupus Anticoagulant

Rivaroxaban Causes False LAC Positive

George reviewed this question posted to the American Society for Clinical Laboratory Science Consumer Web Forum: “After DVT/PE helped by TPA/heparin and now on Xarelto 4 weeks, my first blood draw shows factor VIII 228%, DRVVT screen 126 sec, confirmation 61 sec, normalized ratio 1.96, but hex phase phospholipid normal range and antiphospholipid normal range. […]

Anticoagulant Therapy

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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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