1.   Each time Blue Cross raises its Medex premiums, healthier seniors abandon the product, leaving behind sicker seniors with higher medical bills.

2.   Higher premiums force healthier seniors to drop out, leaving behind sicker patients with larger medical bills.

3.   That would combine sicker seniors who buy drug coverage with healthier seniors who tend to buy medigap plans with no drug benefit.

4.   The problem is that as healthier seniors drop their medigap coverage, only sicker seniors remain, driving up the average costs.

5.   They called for developing a mechanism that would enable Medicare to raise payments to HMOs with sicker senior citizens and to lower reimbursement to health plans with healthier seniors.

6.   Trade groups have also contested any studies that say HMOs enroll healthier seniors.