What I meant by my last sentence is that many times there is "noise" in medicine, and in test results and our first inclination is to ignore that noise. But, sometimes that noise has meaning, and may be a clue to better understand.

We need to know when rapid changes in test results is because there are rapid changes in what we are measuring or because our tests or equipment are inaccurate. We can't assume that something is stable or reproducible when it is not.

A significant problem with evaluation of some patients with myasthenia is that they have rapid changes of what is usually relatively stable.

I hope this makes it more clear,

alice