Nancy Miner, MT (ASCP), who is the Hematology Lead Tech at the Seton Family of Hospitals in Austin, TX, posted this question on Pat Letendre’s Medlab_L list. Nancy gave me permission to post her question on Fritsma Factor:
Our lab is evaluating coagulation instrumentation. We currently use a Diagnostica Stagoinstrument, which uses an electromechanical method for PTT and PT testing. This method is not affected by lipemia and hyperbilirubinemia (icterus). The Beckman ACL TOP 500uses photo-optical methodology that is affected by lipemia and icterus. Is it acceptable to air-fuge samples for coagulation testing in cases of lipemia? What alternative procedures can be used to get results in icteric samples? CAP question HEM.37400 asks this very question. Can anyone using a photo-optical methodology or the TOP 500 give me some insight as to how these samples should be handled? Thanks.
I sent Nancy’s question to Kim Kinney, MT (ASCP), Technical Coordinator for Hemostasis and Thrombosis at Clarian Health Labs (Indiana University) in Indianapolis. Kim had recently validated several pieces of Beckman equipment after switching from MDAs. Here is her response:
Clarian has always used ultracentrifugation for routine tests on specimens that are lipemic. Using it when testing for von Willebrand disease is a bit more controversial. The molecule is so large that it is probably centrifuged out by the high speeds of an ultracentrifuge.
The analyzer reads at a wavelength that avoids interference from icterus. On the rare occasion icterus may be a problem, we use a mechanical clotting method as an alternative to determine results of these samples. By reviewing the clot curves from the TOP analyzer we can gain additional information for troubleshooting and determine if errors are a result of a sample, patient, analyzer, or reagent problem.
I then asked Kim to give specifics on frequency. She responded:
It isn’t very often that the TOP cannot get a result. I would say maybe less than once a month. We have more issues with low fibrinogen samples not giving us a result. These are usually the icteric samples but it is not the color that causes the issue. We usually will look at the clot curve and can give the clinician what we call an “estimated PT/PTT.” We do not give an INR on these samples, only PT and PTT in seconds.
I invite anyone with experience using photo-optical instruments to add their comments. Geo.