No, there is no need to run a calibration check before you do the test. Each iHearTest kit is calibrated before it is shipped. The software will automatically ask you to perform a calibration check after 10 tests.
You can get bad calibration results if the calibration check is performed in a noisy room, or if there is too much vibration - for example: when there is traffic noise, fans, vibrations from people walking in the room, etc. If you are prompted to perform a calibration check - it must be done in a quiet room with the device preferably placed on a soft surface - for example do not put it on a hard tabletop, use a pillow or a soft pad.