Siemens is global hemostasis market leader (app. 40%). Siemens history in haemostasis market had started in 1948 with Behring company name. Nowadays, market for Prothrombin Time (PT) using Owren method is small (app. 5%, mainly used in Scandinavia, Lithuania, Japan), while Quick's PT - 95%. That is why in Lithuania Prothrombin Time test is so often called as SPA (Stago Prothrombin Assay), although that is only a commercial name of PT reagent. The Quick PT is considered the gold standard for the measurement of the Prothrombin Time in global screening and Oral Anticoagulant Therapy (OAT) monitoring, also large international studies that make recommendations for therapy adjustment are based on Quick PT reagents. Despite big competition between Quick and Owren's PT, the international independent studies demonstrated, that both methods do not differ and thus are equally suitable for the global harmonization of INR results in OAT monitoring.