Aetna (AET) reported stronger-than-expected third-quarter sales on Thursday and handily topped on the bottom line as the insurer grew health-care premiums and tightened expenses.

The results led the third-largest U.S. health insurer to improve its full-year outlook.

It now anticipates fiscal 2012 profit of $5.10 a share, to the high-end of its earlier range of $5.00 to $5.10 a share. The consensus is calling for earnings of $5.08.

The Hartford, Conn.–based health insurer posted net income of $499.2 million, or $1.47 a share, compared with a year-earlier profit of $490.4 million, or $1.30.

Excluding one-time charges related to the early extinguishment of debt and the proposed acquisition of Coventry Health Care, Aetna said it earned $1.55, topping average analyst estimates of $1.34 in a Thomson Reuters poll.

Revenue for the three-month period was up 6% to $8.90 billion from $8.40 billion a year ago, narrowly below the Street’s view of $8.96 billion.

“Aetna's strong performance in the third quarter is the result of our diversified business model, and demonstrates the rigor with which we manage our operations,” the company’s CEO, Mark Bertolini, said in a statement.

Shares of Aetna traded up about 2% to $44.79 on Thursday. 

The health benefits provider attributed the quarterly improvement to stronger premiums in each of its commercial, Medicare and Medicaid businesses and tighter costs that helped narrow its business segment operating expense ratio.

Operating earnings in its health-care group climbed to $531.8 million from $525.7 million in the year-earlier period.

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