ARACHnase. An evaluation of a positive control for platelet neutralization procedure testing with seven commercial activated partial thromboplastin time reagents.

ARACHnase (Hemostasis Diagnostics International Co., Denver, CO) is a normal plasma that contains a venom extract from the brown recluse spider, Loxosceles reclusa, which mimics the presence of a lupus anticoagulant (LA). Seven activated partial thromboplastin time (APTT) reagents were used for platelet neutralization procedure (PNP) testing with ARACHnase: Automated APTT (Organon-Teknika, Durham, NC); Thrombofax and Thrombosil (Ortho, Raritan, NJ); Actin and Actin FSL (Dade, Aguado, PR); and Thromboscreen-Kontact and Thromboscreen-APTT LS (Pacific-Hemostasis, Ventura, CA). ARACHnase consistently displayed a positive PNP result of greater than 5 seconds correction of the initial baseline APTT. Thus, ARACHnase may provide a positive control for LA testing, regardless of the choice of APTT reagent and activator/phospholipid combination.