Since September, shares of Thermo Fisher Scientific (NYSE:TMO) have been on a roll, gaining more than 50% to close Friday at $64.93. So can Thermo continue its winning streak or is it time for investors to take some money off the table?

Even with Thermo trading near its 52-week high, it appears there may be some upside. Although the company’s P/E is approaching 25 based on trailing earnings, it’s not that pricey when you consider that’s a discount from its average P/E of 30 over the last five years. Some investors wish Thermo paid a dividend, but it appears the company prefers to pour its dollars into building the business.

The company earlier this year completed the $2 billion purchase of Dionex Corp. The acquisition enables Thermo to capitalize on Dionex’s strength in chromatography instruments, software and consumables and complements its leading positions in mass spectrometry and laboratory information management systems. It also complements Thermo’s strong presence in China, where the company has established the headquarters for its global environmental instruments.

In the fourth quarter of 2011, Thermo expects to complete its $3.5 billion acquisition of Sweden-based Phadia, a pioneer in allergy diagnostic tests and a European leader in autoimmunity diagnostics. Peter Lawson, an analyst with Mizuho Securities in New York, said Phadia is a “neat fit,” meshing well with Thermo’s specialty diagnostic business and moving the company deeper into allergy testing and autoimmune testing.

Not on the scale of the Dionex and Phadia purchases but still significant, last week Thermo acquired Trek Diagnostic Systems to complement the company’s existing portfolio of microbiological testing technologies. Trek serves pharmaceutical and clinical laboratory markets and will be integrated into Thermo Fisher’s Analytical Technologies Segment.

The acquisitions are part of the company’s strategy to bolster its stable of diagnostic products while moving away from services. Thermo recently divested two medical-testing businesses. Aaron Vaughn, an analyst at Edward Jones & Co. in St. Louis, said the company is executing on its plan, using their capital allocation for M&A.

Thermo had been rumored to be eyeing Gen-Probe Inc. (Nasdaq:GPRO), which earlier this month hired Morgan Stanley to find a buyer. However, the purchase of Phadia probably put a kibosh on that potential deal, said Vaughn. He thinks it would be too much for Thermo from a balance-sheet standpoint.

For 2011, Thermo said revenue should be up about a billion dollars from 2010’s sales of $10.57 billion. That would give the company a respectable 6% CAGR in sales during the past five years. It expects to earn an adjusted $4.05 to $4.15, up nearly 6% from a year earlier. During the past five years, the company’s EPS has grown at a 17% CAGR.