From Carol Gizzi at Baycare in Florida, We perform the factor VIII assay with a silica activated APTT ( PTT) reagent. We monitor hemophilic patients. Recently we were asked to switch our reagent to a PTT reagent using ellagic acid as the activator. We do not understand the reason for the request. We thought the silica activated reagent was the most sensitive? Are we incorrect?
Hi, Carol, and thank you for your question. I know of no reason for switching from a silica-based to an ellagic acid-based PTT reagent for the routine monitoring of coagulopathies, and in particular for factor VIII. I attended the Mayo Laboratories Coagulation Conference last week and used the opportunity to discuss this with my colleague, Dave McGlasson, from Wilford Hall USAF Medical Center, who also checked with several reagent distributors, and none knew of any reason. You probably check PTT sensitivity for factor VIII as part of your reagent validation, this should be all you need. It is true that the International Society on Thrombosis and Haemostasis recommends silica-based PTT reagents for the detection of lupus anticoagulant, as they are more sensitive than ellagic acid-based reagents, however both should work fine for monitoring factor deficiencies. Geo.