Methods and apparatus are disclosed for determining a new anticoagulant therapy factor (nATF) for monitoring oral anticoagulant therapy to help prevent excessive bleeding or deleterious blood clots that might otherwise occur before, during or after surgery. In one embodiment, the new anticoagulant therapy factor is based upon a determination of a new fibrinogen transformation rate (nFTR) which, in turn, is dependent on a maximum acceleration point (MAP) for fibrinogen (FBG) conversion. The new anticoagulant therapy factor quantity is also based upon the time to maximum acceleration from the time of reagent injection (TX) into a plasma sample, but does not require the difficulty of obtaining prior art International Normalized Ratio (INR) and International Sensitivity Index (ISI) parameters. Other embodiments provide methods and apparatus for determining an anticoagulant therapy factor without requiring use of a mean normal prothrombin time determination or ISI.