Mixing Studies

Mixing Studies on Anticoagulation

From Dr. King: We are encountering with increasing frequency requests from hematologists to perform mixing studies on patients that are known to be on some form of anticoagulation. My question is regarding the utility of doing such testing. Another aspect to the question is whether you can do testing for a prolonged PTT when the […]

Anticoagulant Therapy

Quick Question: Mixing Studies

From Herb Crown, St. Louis University Hospital Coagulation Reference Laboratory: George, for the mixing study cutoff question, I answered “other” because, as I have written on a number of occasions, we have a reference range for our control and patient mixing studies that is different than our routine aPTT. I hope I did not confuse […]

Unexplained Prolonged PTT

From Dr. Samir Patel: George, I have enjoyed reading the blog for many years now (since fellowship) and am wondering if you could shed some light on a patient I am working up. This is a 90 year old woman who was sent for evaluation after she developed a hematoma post cardiac catheterization (no need […]

Coagulation Factors

Yet More on Promacta

This is from friend and colleague, Dean Willett, Instrumentation Laboratory: Hi, George; A few points to consider… There are two potential sources of interference here: biochemical and optical. Much like hemolysis, if the sample contains biochemical interference, results will be affected regardless of detection method. In the absence of any data it’s not clear if this drug […]

Bleeding Disorders

More on Promacta

From my friend Ali Sadeghi-Khomami, PhD, Precision Biologic Inc: Eltrombopag is a diazo derived compound that acts like pH indicators, i. e., it changes colour at different concentrations of hydronium ions. Thus it is expected that it interferes with chromogenic assays such as the bilirubin assay, especially when assay calibration will not match the colour of the testing sample. […]

Bleeding Disorders

Mixing Studies: What Constitutes Correction?

This week George posts a new Quick Question to learn how we define PTT mixing study correction. Here is how the question will look: When performing PTT mixing studies using normal control plasma (NP), what criterion do you use to define correction? a. Mix result within 10% of NP result b. Mix result within 5 […]

Prolonged PT, Normal Factor Levels

From Joyce Low: We have a patient with a prolonged prothrombin time (PT) and normal partial thromboplastin time (APTT, PTT). He bled, but factor levels were all normal. He’s an 84 year old man here for pacemaker insertion. PT was 19s (Neoplastine; reference interval 11–15s ), PTT 31s (Actin FS RI 25–35s), thrombin time, fibrinogen, and […]

Combined IX and XII Deficiency?

From Dr. Jeanine Walenga, Loyola University Medical Center: George, what could be the reason(s) for a 30 yo female patient having multiple mild factor deficiencies of FIX (64%) and FXII (51%)? The activated partial thromboplastin time (APTT, PTT) was slightly prolonged but corrected with a mixing study. FVIII and FXI were normal. Patient does not have LA […]

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 […]

Uncontrolled Nosebleed

From Gabor Varadi, MD, Albert Einstein Cancer Center: Dear George, I would like to discuss with you a nose bleeding case. The patient is a 55 yo female with history of hepatitis C-induced chronic liver disease, alcohol and cocaine abuse who came to us with left nostril bleeding following finger trauma (nose picking). She does not […]

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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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