A comprehensive laboratory package for evaluating the major blood clotting pathways. This package includes: prothrombin time (PT) and International Normalized Ratio (INR), which assess the extrinsic and common pathway of blood clotting and are dependent on clotting factors I, II, V, VII, and X; partial thromboplastin time (PTT), which assesses the intrinsic pathway and is dependent on clotting factors VIII, IX, XI, and XII; and total thrombin time (TCT), which assesses the common final stage of clotting, namely the conversion of fibrinogen to fibrin. Together, these three tests provide a comprehensive assessment of the function of the coagulation system.