Paced by Accelerate Diagnostics and Bio-Rad, the 360Dx Index beat the broader markets. Shares of GenMark and Opko, however, were sharply down.
Thermo Fisher said that it received notice that TRC Capital made an unsolicited mini-tender offer to purchase up to 1 million shares of its stock at $181.75 per share.
The investment bank gave LabCorp an Outperform rating and a price target on its stock of $175. It gave Quest a Market Perform rating and an $88 price target.
September was the third consecutive month in which the index barely moved month over month. NantHealth paced the gainers, while Quest Diagnostics paced the decliners.
Amid a flat month for the index, some firms saw large swings in their stock price. Natera led the gainers, while NantHealth led the decliners.
The molecular diagnostics firm was told on Wednesday that it is again in compliance with a rule calling for a $1 minimum bid on its share price.
Upgrades from two investment banks appeared to boost Quidel's shares, while a medical policy update from Aetna may have dampened Natera's.
The Index was up about 4 percent month over month and outpaced the Dow Jones Industrial Average and the Nasdaq Composite, but trailed the Nasdaq Biotechnology index.
Along with Exact, Natera and Qiagen saw sharp spikes in their stock prices, while Invitae and Opko Health each saw their share prices drop by more than 20 percent.
First quarter results that blew away analysts' estimates lifted Exact Science's stock, while Abbott's new deal with Alere sparked that firm's share price.