Calendar Update

On June 30, 2009 I updated the calendar of hemostasis and clinical laboratory science-related events and seminars through the summer of 2010. If you know of an event you would like listed, please send me the name, sponsor, location including venue, and dates, and I will be happy to post them. Geo.

Congresa Cientifico Deferred

To our disappointment, the IV Congreso Nacional de Microbiología, scheduled for July 1-3 at the Intercontinental Hotel Tegucigalpa, Honduras, has been deferred because of the political unrest that led to a coup and removal of President Zelaya on Sunday, June 28.  The meeting will be held later when political concerns become stabilized. Please watch here for an announcement. Geo

Quick Guide to Coagulation; 2nd Edition

In shameless self-promotion, I want to announce that our Quick Guide to Coagulation, 2nd Edition is now available from AACC Press and from the American Society for Clinical Laboratory Science. The new edition is expanded from 62 to 108 pages and includes a section on platelet aggregometry and a series of speedy reference tables. The Quick Guide is still designed to fit in a lab coat pocket and is still available for $20.00.

Does Actin FS Introduce a FVIII or FIX Assay Bias?

Here is an interesting question about Actin FS sensitivity for coagulation factors VIII and IX from Vanessa Chan at SickKids Hospital in Toronto:

I’m currently working on the validation of the Stago Sta-R EvolutionÒ. Throughout this process, I have run into a couple of problems with my FVIII and FIX assays. Using Siemens Actin FSÒ, Stago UnicalÒ calibrator and Stago Deficient PlasmaÒ, I was finding a high bias for both factors starting at the 50% and up range. The folks at Stago sent me this article: Pouplard C, Trossaert M, Le Querrec LE, et al, Influence of source of phospholipids for APTT-based factor IX assays and potential consequence for the diagnosis of mild haemophilia B. Letter to the Editor, Haemophilia 2009; 15: 365–8. The authors concluded that Actin FS showed a high bias for factor IX compared to Stago CK PrestÒ and Stago PTTAÒ. The bias was limited to mild hemophilia B patients, those whose FIX levels were between 5 and 40 IU/dL, and to qualitative (type II) deficiencies in which immunoassay and activity results were discrepant.

Because all the trouble-shooting we tried did not solve this problem, we switched to CK Prest and so far (only one week), it has worked well. We ran the NIBSC standard on it and it recovered well. I know other labs use Actin FS as well but perhaps not in the exact combination of reagent, calibrator and control and have had problems. I was wondering if you know anything about matrix or pH interferences between reagents or lyophilized vs. frozen products.

Thank you in advance, George and I look forward to hearing from you.

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Employment in Coagulation Specialty

I want to draw everyone’s attention to Curing and Caring by Matthew Patton in the June 1, 2009 issue of Advance for Medical Laboratory Professionals. Although Mr. Patton’s article appeared in the print issue, it is available online as a PDF, page 12 and 13. The article features Dr. Larry Smith, a contributor to Fritsma Factor, and accurately describes the needs and rewards of a position in the specialty coagulation laboratory. Geo.

Coagulation Factor Characteristics

Two coagulation factor questions from Madan Verma, MLT:

I was cruising through your website and I have two questions:

Do coagulation factors circulate in blood as activated proteins or they are in a non-active form? Is there a certain proportion of activated and non-active?

Factor VII (activated or native form?) has the shortest half life of six hours. Does this mean in vivo or in vitro? We may add PT on a specimen up to 24 hrs, but, while factor VIII has a half life of 12 hrs, a PTT is allowed to be added on a drawn specimen within only four hours. Why?

Thanks in advance, Madan Verma, MLT

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Sekusui Chemical Plans to Acquire ADI

Steve Duff of Precision BioLogic alerted me to this March 18, 2009 news release from American Diagnostica, Inc and Sekusui Chemical Company, Ltd describing Sekusui plans to acquire 100% of ADI. This is a big change for a company with a long US in vitro diagnostics history.

VWF Cleavage Regulation by Shear Force and ADAMTS13

Steve Duff of Precision BioLogic forwarded a reference to a mechanical and enzymatic mechanism that controls the length of von Willebrand factor (VWF) multimers. According to Zhang X, Halvorsen K, Zhang CZ, Wong WP, Springer TA: Mechanoenzymatic cleavage of the ultralarge vascular protein von Willebrand factor. Science 2009;324:1330-4, shear force exerted on the VWF molecule “unrolls” the molecule and exposes a portion of the A2 domain to the WVF-cleaving protease ADAMTS13. Ultra-large VWF multimers (ULVWF), tethered to the endothelial cell from which they originated, are more easily unrolled and cleaved than small multimers. Their length and ability to be cleaved make VWF molecules part of hemostasis control. The experimental model described involves some intriguing microtechnology termed “laser tweezers.”

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