GREENVILLE, SC — For almost 28 years, Dr. Carolyn Fields ran her primary care practice on her own. Along with treating diabetes, curious rashes and stomach bugs, she hired the staff and managed payroll. But in June, she became an employee of Bon Secours St. Francis Health System. "I didn't want to be bought. I wanted my independence," she said of her earlier practice days. "But it's becoming more and more difficult. And I got tired of all that." It's happening in the Upstate and across the nation — hospitals are acquiring more physician practices as they prepare to move away from a fee-for-service reimbursement system that pays for services and treatments to one that focuses more on quality outcomes and containing costs.