Still More on False Positive Hex-phase Phospholipids

The topic of hex-phase phospholipid neutralization tests that turn up positive for lupus anticoagulant in people who have specific anti-factor VIII inhibitors keeps coming back. Here is a comment from Dr. Jay Lozier of the NIH that takes us down a new pathway, the prevalence of transient lupus anticoagulants during acute inflammatory events… Dear George, I have recently stumbled upon your […]

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Jan 24 2011

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Answers to RVV Questions

Back to our earlier discussion of the old Russell viper venom time (RVV, not the “new” dilute Russell viper venom time, DRVVT). Joe Lamb came up with the name, Stypven Time. The purpose was to differentiate between a factor VII deficiency (prothrombin time prolonged, DVV normal) and factor X deficiency (both long). With improvements to the partial thromboplastin time and […]

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Back to the Falsely Elevated Anti-Xa

I was intrigued by the comments related to dextran sulfate added by Gary Bullard andHerb Crown to the falsely elevated anti-Xa discussion that started with a question from an unknown participant on January 17, 2011. Though both Gary and Herb indicated that dextran releases heparin from endothelial cells, I wondered if dextran’s polysaccharide structure could directly interact in the anti-Xa reaction, substituting […]

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PTT Prolongation Limit and Mixing Studies

I received the following question from Dr. Robert Gay at Greensboro Pathology Associates, Greensboro, NC: It makes sense not to perform a mixing study when the partial thromboplastin time (PTT) is just above the reference range but what is commonly used as a cutoff? Is there a way that individual labs can establish what their limit should be? […]

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More on False Positive Hex-phase Phospholipid Tests

On November 29 I attempted to answer the following question from G Pihan of Beth Israel Deaconess Medical Center in Boston: “What is the incidence of false positive hexagonal phospholipid neutralization tests in the presence of a strong (400-800 BU) factor VIII inhibitor?” Click on False Positive Phospholipid Neutralization to see the discussion, which was lengthy and inconclusive. I had distributed […]

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PT Specimen Clotting: Cold Agglutinin?

From “Pathous222″ Greetings. We recently encountered a specimen problem. A 64 YO lady on coumadin for patent foramen ovale came in as an outpatient for a prothrombin time (PT). The blue top clotted. We recollected it, collecting two tubes this time. One clots and the other appears to be OK but the PT is greater […]

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Any Relationship Between RVV and D-dimer?

From Vilas Hiremath: Hello, I have spiked normal pooled plasma with crude Russell viper venom (RVV) in different concentrations. The D-dimer is negative. Your comments please. Hello again,Vilas Hiremath, and thank you for another thought-provoking question. I know of no reason to anticipate a positive D-dimer from a clotting assay on normal plasma, be it […]

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Shortened PTT and Mixing Studies

From “plovejoy:” Is there a reason one might perform a partial thromboplastin time (PTT) mixing study on a patient whose initial PTT result is short (slightly below the reference range)? Since a short PTT time would appear to indicate there isn’t a factor deficiency or a circulating anticoagulant, might there be another reason? I couldn’t […]

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Reptilase Time and Heparin

Debbie Moffitt from Honolulu posted a question on Pat LeTendre’s Medlab_L earlier this month: A hematologist is asking for the reptilase time test to distinguish when prolonged partial thromboplastin time (PTT) and thrombin time (TT) results are due to heparin. When heparin is suspected, we use Hepzyme to try to correct the TT or PTT . We also review […]

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POC Assay for Dabigatran

George: We are getting a lot of questions about monitoring Pradaxa (dabigatran) and it keeps coming back to the Ecarin clotting time (ECT). Do you know of any POC testing kit or instrument that could be used to monitor this drug’s effect on a patient’s clotting? Thanks, Terry Black Teresa Black, MT(ASCP) Senior Medical Technologist […]

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Still More on False Positive Hex-phase Phospholipids

Answers to RVV Questions

Back to the Falsely Elevated Anti-Xa

PTT Prolongation Limit and Mixing Studies

More on False Positive Hex-phase Phospholipid Tests

PT Specimen Clotting: Cold Agglutinin?

Any Relationship Between RVV and D-dimer?

Shortened PTT and Mixing Studies

Reptilase Time and Heparin

POC Assay for Dabigatran

George Fritsma MS MLS

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