A computer implemented method, system, and/or computer program products derives a medical diagnosis for a patient. A current description of a patient is matched to a cohort of persons who each have a substantially similar description as the patient. Possible medical diagnoses, which have been accurate for members of the cohort, are presented for the patient. If one of the secondary medical diagnoses has an unacceptably high potential for an unacceptable outcome if improperly treated, then additional tests are run to rule out that secondary medical diagnosis.