Rapid INR Rise in Pneumonia

From Michael Huang, MicroPoint Bio: An 80 yr old male on warfarin was admitted to A&E of a local hospital for the complaint of shortness of breath. Lab test results showed INR of 15 after his admission. Just 8 hours before, the POC instrument his doctor used to monitor his INR showed a reading of 2.6. The […]

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Anticoagulant Therapy

Feb 21 2013

george

High HCT and PT, PTT, and D-dimer

From Barbara Robinson, MT (ASCP), Children’s Hospital of New Orleans, If a sample is tested for D-dimer, prothrombin time (PT) and partial thromboplastin time (aPTT, PTT), and the anticoagulant in tube has not been adjusted for high hematocrit (HCT = 60.8%), what tests would be invalid, and how would results be affected? Hi, Barbara, and thank you […]

Screening Assays

Factor II Assay in Place of INR?

From Kelly Townsend at TriCore Reference Laboratories: We have several patients in whom the INR does not appear to accurately assess their anticoagulation status. Since we do not have the chromogenic factor X assay on our menu, we’re interested in using the factor II activity assay based on a poster presented at THSNA meeting by the Univ of […]

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Anticoagulant Therapy

Feb 13 2013

george

More on PT Validation and AMR

Here’s an additional note confirming Denise Solieau’s February 12 discussion of PT validation and analytical measurable ranges (AMRs). Page 83 of the July 31, 2012 CAP survey references the value of AMRs in coagulation testing and includes this statement, “The new checklist requirements (meaning AMR) apply to hemostasis test methods that are calibrated and directly measure the concentration or […]

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Anticoagulant Therapy

Dec 28 2012

george

Platelet Function Testing and the Bleeding Time

In 2009 Dave McGlasson and I published McGlasson DL, Fritsma GA, Whole blood platelet aggregometry and platelet function testing. Semin Thromb Hemost 2009;35:168–80. This article, the second-most cited in the 2009 Seminars in Thrombosis and Hemostasis, reminded me of our Quick Question about the Ivy bleeding time posted in early November, and subsequently lost when our site crashed […]

Bleeding Disorders

Why Are PT & PTT Normal in Dysfibrinogenemia?

From Tania Puro, first posted on November 14: Can you explain why the activated partial thromboplastin time (APTT, PTT) and the prothrombin time PT are normal in dysfibrinogenemia? Hello, and thank you for your question. Dysfibrinogenemia is a qualitative or functional fibrinogen deficiency associated with moderate to severe liver disease. The liver produces normal or even […]

Screening Assays

Does In Vivo Citrate Affect PT or PTT?

From Madan Verma: Hi George. I am wondering if there are any correlation studies about whether switching hemodialysis patients from heparin to 4% sodium citrate will affect the prothrombin time (PT) or partial thromboplastin time (PTT). Thank you. Hello, Madan Verma, and thank you for your patience. I found over 500 PubMed references, most of which […]

Screening Assays

Do APAs Affect the PT?

From Scott Miller, St. Mary’s of Michigan Medical Center. Is there any consensus on whether anti-phospholipid antibodies (APAs) like lupus anticoagulant (LA) have any effect on prothrombin times and international normalized ratios (PT/INRs)? We have a patient who has been tested positive in the past for LA, and her INRs consistently run a bit higher in the […]

Lupus Anticoagulant

Do APAs Affect the PT?

From Scott Miller, St. Mary’s of Michigan Medical Center. Is there any consensus on whether anti-phospholipid antibodies (APAs) like lupus anticoagulant (LA) have any effect on prothrombin times and international normalized ratios (PT/INRs)? We have a patient who has been tested positive in the past for LA, and her INRs consistently run a bit higher in the […]

Lupus Anticoagulant

PEG-ylated Drugs and Clotting Assays

From Vanessa Chan, Sick Kids Hospital in Toronto: Hi George, Do you have any information on how PEG-ylated drugs (PEG-ylated to increase the half life of the drugs) may affect clotting assays? Thanks! Vanessa. Hi, Vanessa, While I have heard that polyethylene glycol (PEG) in drugs can affect the phospholipid structures in prothrombin time (PT) thromboplastin reagent and […]

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Anticoagulant Therapy

Screening Assays

Rapid INR Rise in Pneumonia

High HCT and PT, PTT, and D-dimer

Factor II Assay in Place of INR?

More on PT Validation and AMR

Platelet Function Testing and the Bleeding Time

Why Are PT & PTT Normal in Dysfibrinogenemia?

Does In Vivo Citrate Affect PT or PTT?

Do APAs Affect the PT?

Do APAs Affect the PT?

PEG-ylated Drugs and Clotting Assays

George Fritsma MS MLS

Cheat Sheets from George

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