Matrix interface for medical diagnostic and treatment advice system and method

An automated medical diagnostic system and method are disclosed. In an embodiment of the system and method, a matrix of cells is displayed via a graphical user interface on a computing device, each cell being representative of a patient health item (PHI) associated with a particular disease. A PHI is entered on the display in one of the cells and a differential diagnosis is updated based on the input PHI. The updated differential diagnosis is then displayed to a user. The system includes multiple diagnostic functions that use the matrix for input and output, wherein the diagnostic functions are selectively executed according to each newly input PHI so as to result in the differential diagnosis. In certain embodiments, the input PHIs are stored in a patient medical record. The computing device can operate independently or in a connection with a system server.