NEW YORK (AP) ¿ Shares of Sequenom Inc. crashed in premarket trading Thursday after the company said it will delay launching its Down syndrome test because of "employee mishandling" that the company said appeared to affect all studies of the test.

Early studies of the SEQureDx test were overwhelmingly positive, but based on Wednesday's announcement, Sequenom will wait for results of independent clinical trials of the test before launching the test instead of relying on its own research.

Some analysts and investors previously had cautioned that all the completed tests were done by Sequenom itself and not outside researchers.

In a conference call late Wednesday, President and Chief Executive Harry Stylli said Sequenom suspended four employees in connection with the mishandling. He also said the company has contacted the Securities and Exchange Commission and Food and Drug Administration.

A new committee has been placed in charge of clinical studies of Sequenom's prenatal diagnostic tests.

Sequenom said it still hopes to launch DNA- and RNA-based versions of the test but will begin sales only after the results of the large and independent studies, already under way, are published in a peer-reviewed medical journal.

Stylli said the independent trials of the test involve about 15,000 women, compared with 858 in the earlier studies. He said the studies are likely to be completed in early 2010. Sequenom said it hopes to have a "validated test" in the fourth quarter.

The San Diego company had planned to launch the test in June.

In heavy premarket trading, its stock plunged $11.60, or 77.8 percent, to $3.31. Sequenom shares finished at $14.91 on Wednesday, and they have traded between $6.10 and $29.14 over the last year.

Junaid Husain, an analyst for Navigator Research, downgraded the stock to "Hold" from "Buy" based on the news.

"Disconcertingly, all (Down syndrome) clinical performance data is presumed to be at risk," he wrote. He said the launch of SEQureDx could be delayed by 12 to 18 months.

The company also reported its first-quarter results late Wednesday. Sequenom posted a larger loss and less revenue than analysts had expected.

Sequenom did not immediately return calls seeking comment.

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