Which action is crucial when performing safety checks before treatment starts?

The correct choice focuses on ensuring that the dialysis machine is on the home screen before starting treatment. This step is crucial because it indicates that the machine is ready for operation and that the operator can access all necessary settings to begin the treatment process safely. The home screen typically provides essential information, such as patient identification and machine status, which are vital for confirming that everything is in order before proceeding.

While rechecking patient medical history, ensuring the machine has been serviced, and confirming patient comfort levels are important steps in overall patient care and machine maintenance, they do not directly relate to the immediate operational readiness of the dialysis equipment. Being on the home screen signifies that the machine has powered up successfully and is functioning properly, setting the stage for a safe and efficient treatment session.