Health insurer Aetna (AET) reported a drop in earnings on Thursday as health care costs rose during the quarter. The company issued full year guidance below analyst forecasts. The nation's No. 3 health insurer said Q4 EPS dipped 3% to 94 cents, falling 2 cents shy of analyst estimates. Revenue rose 6% to nearly $9 million, in line with projections. Aetna ended 2012 with 18.2 million members, with 64,000 members joining during the quarter. Shares