Intravascular diagnosis apparatus and methods are disclosed. In one aspect of the disclosed technology, a intravascular diagnosis apparatus includes a monitoring guidewire and a display unit. The monitoring guidewire includes a core wire and a sensor disposed in a distal region of the core wire. The display unit includes a processor and a display screen, and is capable of receiving communication from the monitoring guidewire. The display unit is configured to perform computations using the processor based on communications received from the monitoring guidewire and is configured to display information on the display screen based on the computations. The display unit can be configured to be disposed after a predetermined number of uses or after a predetermined duration of use.