A method for determining quality of a communications link between an external instrument (EI) and an implantable medical device (IMD) is provided. The method includes receiving, with a receiver of an EI, data packets sent at intervals from an IMD and determining, with a processor of the EI, an expected time interval between a first data packet and a second data packet. The processor of the EI determines a difference between the expected time interval between the first data packet and the second data packet and an actual time interval between the first data packet and the second data packet. The processor of the EI also provides a time variant communication quality indicator based on the difference between the expected time interval between the first data packet and the second data packet and the actual time interval between the first data packet and the second data packet.