Thrombogenic properties of prothrombin complex concentrates.

In a recent paper White et al.’ reported that the thrombogenic properties of prothrombin complex concentrates (PCC) are due to the presence of factors IXa and Xa. The presence of these activated factors, however, was detected indirectly by applying different inhibitors, e.g., a specific seryl reagent, phenylmethylsulfonyl fluoride (PMSF). They concluded that the effect of PMSF is due to the inactivation of factor Xa and not to that of factor IXa. Factor IXa is a serine-protease.2 It should therefore be susceptible to the seryl reagent PMSF. We have found with purified human