Cowen & Co.

(COWN) - Get Report

is dropping coverage of some big medical-sector companies amid questions about the integrity of research by a senior analyst.

Cowen has terminated senior health care analyst Dhulsini de Zoysa, who covered big names including

Biomet

( BMET),

Boston Scientific

(BSX) - Get Report

and

Medtronic

(MDT) - Get Report

.

In a note issued to clients, Cowen says it terminated the analyst "in connection with an internal review relating to the reliability of certain ... previously published research reports."

A Cowen spokesman says the company began a review of previous research reports after learning of questions about their trustworthiness. The spokesman declined to specify which reports were questioned or to describe the nature of the problems with the research.

"The analyst who prepared these reports has been terminated," the firm said, "and we intend to transition coverage of these companies to other Cowen analysts in the near future."

Calls to de Zoysa's residence in Manhattan were not immediately returned. The medical supply analyst was hired in May 2004 and terminated on Aug. 27, according to a Cowen human resources representative. The analyst had been on maternity leave when issues tied to her biotech research emerged.

According to Cowen's Web site, de Zoysa is a Harvard College grad who joined Cowen as a senior analyst from Fulcrum Global Partners. She also had a stint as a Washington lobbyist and worked at Salomon Smith Barney.

De Zoysa also covered

Northstar Neuroscience

( NSTR),

Smith & Nephew

(SNN) - Get Report

,

St. Jude Medical

(STJ)

,

Stryker

(SYK) - Get Report

,

Volcano

(VOLC)

,

Wright Medical

(WMGI) - Get Report

and

Xtent

(XTNT) - Get Report

.