Natera

Of the 27 companies in the index, 14 firms' stocks were down, while 13 companies' share prices increased.

A bi-weekly listing of recent local coverage determinations from Medicare Administrative Contractors.

The company beat analyst estimates on the top and bottom line, driven by sales of its Panorama noninvasive prenatal and Horizon carrier screening tests.

Other big gainers last month included Accelerate Diagnostics and Natera, and share prices of 23 of the 27 companies in the index increased month over month.

The broader market drove down the stock prices of many diagnostics companies. Natera, Guardant Health, and CareDx paced the gainers.

The company's first quarter revenues were driven by sales of its noninvasive prenatal screening and carrier screening tests.

The firm is selling more than 5.2 million shares at an offering price of $19 per share.