Communication sessions between external devices and implantable medical devices are tracked using a session value that is incremented for each new session and that is stored within the implantable medical device. The database loader uses SQL flags, historical information gained from monitoring prior query execution times and patterns, and node and network configuration to determine how to effectively cluster data attributes across multiple nodes. According to a preferred embodiment of the method of the invention, a sample containing an enzyme of interest or a microorganism associated with the enzyme is combined with a suitable substrate, and a fluorescent product of the enzyme-substrate reaction is selectively detected. The spacer has a hole opened at the center portion thereof, and a bolt seat surface and an inclined surface on the outer panel side.