Health insurer Cigna Corp. (CI) on Wednesday reported its quarterly net profit almost doubled, helped by the sale of its retirement unit, but its 2005 profit outlook fell short of analyst expectations.

The fourth-quarter earnings soundly topped Wall Street estimates, but analysts were unsure whether the gain reflected improvements in its health insurance operations.

Shares of Cigna (search), which has been attempting to right itself after losses in recent years as it struggled to price its premiums correctly, fell slightly in premarket trade.

Net earnings rose to $558 million, or $4.16 per share, in the fourth quarter, from $281 million, or $2.00 per share, a year earlier.

Philadelphia-based Cigna reported income from continuing operations before items of $323 million, or $2.41 per share, compared with $224 million, or $1.59 per share, a year earlier.

Wall Street analysts polled by Reuters Estimates forecast earnings of $1.59 per share in the fourth quarter.

Cigna did not provide figures on a key measurement known as prior period development, which measures funds set aside based on lower-than-expected medical costs in past quarters. Analysts said that left them wondering how much of the improvement came from operations versus the prior reserves.

"I'm a little cautious about the quality of the earnings," said Williams Capital Group analyst Adam Miller. "At first blush, it looks like they had a blow-away quarter, but I want to know how much of that is prior period development versus actual operational improvement."

Cigna's comeback is partially dependent on stemming enrollment losses. Membership in the company's health plans was down 16 percent at 9.7 million at year-end 2004 from a year earlier, and down from a peak of 13.4 million in 2001.

Consolidated revenues declined slightly to $4.3 billion from $4.5 billion a year ago. Premiums, which fuel much of revenue for HMOs, fell to $3.4 billion from $3.8 billion a year earlier as Cigna continues to cull membership.

For 2005, the company forecast earnings of $5.55 to $6.05 per share before items, below Wall Street average estimate of $6.22.

For the first quarter, including stock option expenses but excluding special items, Cigna sees $1.35 to $1.55 per share. That compares with average analyst views of $1.50 per share.