UPDATE 1-Hologic device effectiveness unclear -- FDA panel

(Adds comments from panel members, context, byline)

By Kim Dixon

GAITHERSBURG, Md. Dec 13 (Reuters) - A U.S. expert advisory panel expressed concerns on Thursday about whether an experimental sterilization device made by Hologic Inc (HOLX.O: Quote, Profile, Research, Stock Buzz) is effective, calling the company's data inconclusive.

Although the advisers to the U.S. Food and Drug Administration said the device is generally safe, a majority had doubts about whether the company's stated "success rate" in preventing pregnancies can be generalized to the population, because of problems with the study's design.

The panel is considering the merits of the device system, called Adiana, which uses a catheter to implant a silicone device in the Fallopian tubes to prevent pregnancy.

The FDA is not bound to accept the advice, but typically it does.

"There is some difficulty with a risk-benefit analysis because of a concern about the benefit, and the effectiveness of this technology," said the panel's acting chairwoman, Marcelle Cedars of the University of California.

The panel conceded the company met a pre-specified study goal of a less than 5 percent pregnancy rate.

The panel did not take official votes on the device, which is not its typical practice.