Abstract: An instrument for use with a patient who is experiencing acute ischemic stroke, the instrument for indicating whether to administer thrombolytic therapy to the patient after a predetermined elapsed time since onset of symptoms has passed, the instrument including an input device through which a user enters clinical information about the patient who is experiencing acute ischemic stroke; and a processor module programmed to use the entered clinical information to compute a predicted benefit to the health of the patient as a consequence of administering thrombolytic therapy to the patient at an onset to treatment time (OTT) that is greater than a predetermined time, the predicted benefit being derived from the entered clinical data.