Like you, I was slow to respond to Gleevec. My local Onc(who I really like, but, has only 1 other CML patient) got concerned that after 18 months I hadn't reached MMR and switched me to Sprycel(I'm still responding slowly). At another forum user's urging, I traveled to the west coast for an appt. with one of the true CML experts. When I told him about my seemingly slow progress and my Onc's concern, he and his nurse grinned and said "Sounds like they were listening to a drug rep(salesperson)". The CML Doc told me to pay attention to the "trend" of your PCR. As long as it's downward, you're improving.
AFAIK (As Far As I Know) very few labs use the latest International Standards. What we get is a 'Qualitative" report more than a 'Quantitative" measurement. The long-term 'trend' is the key.
Hope this helps a little.