BlueCross BlueShield of Tennessee has rolled out an online tool that provides cost and quality information on doctors to nearly 2 million of its members. Members of the insurer can now see information such as what other physicians billed for procedures within a certain specialty. They also can see a doctor's record on whether he performed screenings that include things such as mammograms or a test for cervical cancer. But the new tool, and others like it, has drawn concerns from some doctors about whether that information ultimately could be used to steer consumers to the cheapest doctors, who may not necessarily be the best.