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Two New Modules

Our newest continuing education modules, Method Validation 1 and Method Validation 2 were posted today, November 20, 2007. Please have a look and if you have any questions, contact me through “Ask George.” I hope you enjoy the modules. Geo.

Why all the PTTs?

It seems that many North American institutions are moving more and more to the use of low molecular weight heparin… …(mostly Lovenox in the US) and pentasaccharide (Fondaparinux, Arixtra) in place of standard unfractionated heparin. Yet, the lab volume of partial thromboplastin time (PTT, APTT) tests seems to be holding steady. What are all those […]

Intravenous Lovenox and PTT: Response

In response to Dana Haas’ question about IV Lovenox (Enoxaparin, low molecular weight heparin, LMWH) and the PTT, while it is true the PTT is relatively insensitive to LMWH, it is slightly prolonged. According to Lovenox Prescribing Information, a standard IV bolus of 30 mg followed by a 1 mg/kg SC injection results in a […]

Intravenous Lovenox and PTT

Dana Haas at St. Luke’s Episcopal Hospital in Houston, TX asks about the effect of Lovenox on the ACT and PTT… In our institution they have started giving patients Lovenox through IV lines (just one shot, not a constant infusion) for patients going for heart catherization. MDs have noticed that Lovenox is prolonging their ACTs […]

Discard Tubes for Factor Assays

Donald R. Peven, MD, of Pontiac, MI extends the question of discard tubes to their use for factor assays. He writes… What is the current practice concerning drawing a waste tube before coag specimens when doing venipuncture? Our understanding is that the NCCLS (CLSI) guideline says that it is OK to draw PTs and PTTs […]

Does Aspirin Block All Platelet Activity

Janice Richardson asks, “I know that once you have taken aspirin, a platelet cannot produce thromboxane A2. Can this same platelet be activated in another way, say through the thrombin receptor on the platelet? Thanks for your help.” Thank you for your question, Janice. Yes, aspirin acetylates platelet cyclooxygenase and slows thromboxane A2 production. Thromboxane […]

The Effect of Argatroban on Factor Assays

On September 22 I received an e-mail question from “JLile” asking if Argatroban affects the outcomes of coagulation factor assays. Argatroban (Novostan) is an intravenous direct thrombin inhibitor indicated as an alternative to heparin in patients suspected of developing heparin-induced thrombocytopenia with thrombosis (HIT). The laboratory monitors argatroban using the partial thromboplastin time test (PTT, […]

Dengue Fever and the PTT

Sachin Kale, MD of Aurangabad, Maharashtra, India asks about prolonged partial thromboplastin time (PTT, APTT) results in children with dengue fever. Here is his question… Hello Everybody, Here, we are getting many children with suspected dengue, they are having thrombocytopenia, normal or near normal PT and prolonged aPTT (more than 2 times control). I have […]

Pentapharm Pefakit FXIII Incorporation Assay

Pam, I may have found an alternative factor XIII assay that helps answer your September question. Centerchem… in Norwalk, CT distributes the Pentapharm Factor XIII Incorporation Assay. The assay uses the “Kohler” technique, “based on the incorporation of the amine substrate 5-(biotinamido)pentylamine (BAPA) into immobilized fibrinogen by thrombin activated factor XIIIa. The incorporated BAPA is […]

Adjusting for Hematocrit

CLSI Standard H-21A4 requires citrate volume adjustment when the hematocrit exceeds 55%. Yesterday, Terry Kotrla, MS MT (ASCP) BB, chair of the MLT program at Austin Community College posted a thought-provoking reference on Medlab-L, a 2005 MLO article by Roy Midyett elucidating and challenging this practice. I am curious about how we go about managing […]

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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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