Ahead of the Bell: Shares of Athenahealth slide

Shares of Athenahealth Inc. tumbled in premarket trading Friday, a day after the medical billing and records software maker reported 18 percent earnings growth in the third quarter but still missed some analysts' expectations.

The Watertown, Mass., company said Thursday after markets closed that its net income for the three months that ended Sept. 30 climbed to $6.2 million, or 17 cents per share, from $5.3 million, or 15 cents per share, in last year's quarter.

Adjusted earnings, which don't count items like stock-based compensation expense, came to 30 cents per share.

Analysts surveyed by FactSet expected, on average, earnings of 26 cents per share.

But Jefferies analyst David Windley said the company's earnings fell a penny short of Wall Street expectations when they were adjusted for a 5 cents per share benefit tied to the company's acquisition of Proxsys LLC, which provides cloud-based care coordination services between doctors and hospitals.

Revenue jumped 26 percent to $105.8 million, but that fell short of Wall Street forecasts for $109.3 million.

Windley lowered his Athenahealth rating to "underperform" from "hold" and his price target on the stock to $60 from $85. He said in a Friday morning research note investors will likely sell shares based on the company's third-quarter performance, but the severity of this sell-off will be limited as they wait for the company's annual investor meeting on Dec. 6 and its 2013 earnings guidance.

Company shares tumbled $6.57, or 8.2 percent, to $73.50 in premarket trading Friday. If that price carries over into regular trading after the market opens, they would be down 25 percent from their 52-week high of $97.37 set in early August.