In US and Canada: For Research Use Only. Not for Use in Diagnostic Procedures. Chromogenic assay for the measurement of Protein C (PC) activity in human plasma, following activation with Protac, a specific enzymatic activator extracted from snake venom (Agkistrodon C. Contortrix). Automatic or Manual method. Liquid Reagent Technology (LRT): all the reagents are in the liquid presentation. Ready to use.