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The iSTAT Kaolin ACT

I have a provocative question about the activated clotting time (ACT) assay from my friend and one-time student Jeanine Walenga PhD, at Loyola University Medical Center in Maywood, IL. I don’t know a lot about iSTAT’s ACT so am posting this for general feedback.

Dr. Walenga writes: We are validating the iSTAT kaolin ACT hospital-wide. All clinical sites will change from the Hemochron 801, Signature Jr, or HemoTec ACT II to the iSTAT, which means most will convert from a celite- to a kaolin-based ACT. We are running patient samples at each clinical site for comparison of clot times between current system and iSTAT. Not surprisingly, the paired values throughout the heparinization period do not match.

My questions/concerns are the following:

Has your hospital made a switch from celite to kaolin for the ACT?
If so did you have any issues during with the conversion?
Did the clinical decision-making threshold points of the ACT differ?  For example, did the clot times for high heparin levels during the procedure; or low heparin levels at the time to pull sheaths different between kaolin and celite ACTs?
Did the doctors have any issues with the conversion?
Jeanine, I’ve found one article from the Baylor group that partially addresses the conversion issue: Schussler JM, Aguanno JJ, Glover EN, et al. Comparison of the i-STAT handheld activated clotting time with the Hemochron activated clotting time during and after percutaneous coronary intervention. Am J Cardiol 2003; 91:464-6. It mentions that in addition to the activator, the end-point for the iSTAT ACT is chromogenic rather than clot-based. Though the article reports adequate correlation, it is no surprise that the therapeutic ranges and decision points would differ given the technology.

Many of us are converting to the iSTAT because it is designed to offer nearly all the routine point-of-care assays so POC personnel need learn only one platform.

Good luck in your conversion next week, and if anyone has any pointers, please send them to Dr. Walenga through Fritsma Factor as soon as you can! Geo

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