Updated from 9:41 a.m. EDT.

Cigna ( CI) said on Thursday that first-quarter earnings more than tripled, but the insurer also saw a decrease in membership and lowered its full-year outlook.

Revised guidance sent shares down 6% in afternoon trading to $19.57.

Earnings during the quarter increased to $208 million, or 76 cents a share, compared with $58 million, or 20 cents, in the year-ago period. Excluding items earnings were 87 cents a share, missing analysts' forecast of 90 cents.

Revenue grew 4% to $4.77 billion.

Cigna projected full-year earnings of $3.70 to $3.90 a share, down from a previous forecast of $3.95 to $4.25.

On Wednesday, rival Aetna ( AET) inked a 1% increase to $438 million, or 95 cents a share, compared with $432 million, or 85 cents, in the year-ago period, perfectly matching Wall Street's expectations.

According to an April 16 article on TheStreet.com, there has been speculation that Aetna is interested in purchasing Cigna for as much as $32 a share.
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