The copy of the draft standard IEC62353 "Medical Electrical Equipment - recurrent test after repair of medical equipment" I have makes interesting reading. It's adapted from the Austrian E 8751-1 standard - the basic philosophy is to apply safety tests that do not damage the IUT, ensure the safety of the person doing the testing and the number of tests that determine safety are minimised to those that are most important, reproducible and comparable. Interestingly it doesn't prescribe an earth-bond test current (yet).
In my opinion, for earth-bond tests to be reproducible and comparable between tests, then 4-wire resistance measurement, using a calibrated device that doesn't require nulling by the operator, is the way to go.
