I'm indebted to Dr. Don McCanne for the following observation:
Government Accounting Office
January 2012
Medicare Advantage
CMS Should Improve the Accuracy of Risk Score Adjustments for Diagnostic Coding Practices
We found that diagnostic coding differences exist between MA plans and Medicare FFS and that these differences had a substantial effect on payment to MA plans. We estimated that risk score growth due to coding differences over the previous 3 years was equivalent to $3.9 billion to $5.8 billion in payments to MA plans in 2010 before CMS’s adjustment for coding differences. Before CMS reduced 2010 ...