Tanya,
Alastair and Sandy are absolutely correct. There is no difference in your results.
In fact, any PCR measure below 0.01% is indistinguishable from PCRU (i.e. 'undetected'). Many false positives can occur below this level. The 'third' decimal place is irrelevant and I wish the reporting labs would stop listing it. It's meaningless.
You could have a string of results: 0.0018, 0.0019, 0.0020, 0.0021 and they mean nothing in terms of trend.
The only trend that matter is if you experience a log increase from one test to the next. For example, if your results went from 0.0019 to 0.02, or higher. Then I would want to investigate alternatives - and then only if there is a follow-on trend up, from 0.02 to 0.2.
You could consider changing TKI drugs to manage side effects, however. Given your outstanding response on Gleevec, you could consider changing to a very low dose Sprycel (20 mg) for therapy maintenance. Chances are it will keep you at a functional PCRU. I take 20 mg Sprycel. I have no side effects I can feel. And I am PCRU (at least until my latest test result comes back!).
Lower Gleevec dose further is another option, but Gleevec is more dose dependent than Sprycel.
Overall you are doing Fan-tab-u-lous. Congratulations!
(and yes, Romo - that is a word)