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PTT Reagent Selection

For those who participated in our summer, 2011 questionnaire (designed by Precision BioLogic’s marketing analyst Mr. Ankush Randhawa) about the choice of PTT reagent relative to its application and sensitivity to lupus anticoagulant, the results now appear in Fritsma GA, Dembitzer FR, Randhawa A, Marques MB, Van Cott EM, Adcock-Funk D, Peerschke EI. Recommendations for appropriate activated partial thromboplastin time reagent selection and utilization. AJCP 2012 137:904–8; doi:10.1309/AJCP3J1ZKYBFQXJM. It appears that some of us are using lupus anticoagulant-sensitive PTT reagents for our routine coagulopathy screening or heparin monitoring. Please click the link to see the abstract with recommendations, or if you have a subscription to the American Journal of Clinical Pathology, you can see the complete manuscript.

I also wish to thank Chris Ferrell of Seattle for her comments on the article, and for an interesting bit of history:

Hi George, Just read your article in AJCP. It was very informative and relevant for every single coagulation laboratory. Great job! The four recommendations at the end were quite thought provoking. I remember back to the 70s and 80s when we had quite a selection of high- and low-LA responsive PTT reagents in the marketplace. It was very confusing to the smaller labs as to which PTT reagent to use when. Many of them were using an inappropriate reagent for their patient population, sometimes because their purchasing department wanted them to use the cheapest and not necessarily the best reagent. That practice still goes on today.

When I worked for Sigma Diagnostics, I got to meet the research scientist who invented Innovin. She had moved to Sigma from Dade. If I remember correctly, her name was Pamela Harker. She was the grand dame of coagulation reagents. She told me something that I’ve always remembered about PTT reagents. There are only 3 things that go into making a PTT reagent. One controls the factor sensitivity, another controls the lupus sensitivity and the third controls the heparin sensitivity. If you change one of the three, it always changes the other two. So, no matter how hard you try, you can’t make the perfect PTT reagent.

Watch for your July issue of AJCP, as Dr. Shetty from Mumbai has responded with a letter to the editor expanding on the issue of PTT reagent LA sensitivity.

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