Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of medical laboratory and research company PAREXEL International (Nasdaq: PRXL) are flying higher by 18% today following the company's second-quarter earnings results and an analyst upgrade.

So what: Today's move is a little surprising given that PAREXEL reported a quarterly profit of $0.23, which was in line with expectations, but revenue fell short of what analysts had expected ($333.2 million vs. $334.3 million). The company also narrowed down the full-year EPS and sales guidance ranges it had previously provided. PAREXEL now forecasts 2012 earnings per share to be in the range of $1.09-$1.17 from its prior view of $1.07-$1.22 and sales of $1.36 billion to $1.38 billion. BB&T Capital Markets took these results as reason to upgrade the stock to buy from neutral.

Now what: I take it back -- today's move is way beyond confusing. PAREXEL did nothing more than tighten its earnings and sales ranges, which did nothing more than put it in line with Wall Street's expectations. If anything, it came in light on its second-quarter sales figures. The analyst upgrade is just as confusing and could be a big reason why the stock is moving so much higher today. As I've often said, analyst upgrades and downgrades are short-term market movers and shouldn't factor into your investment thesis on a stock. But after a move like we're seeing today, I think all the value has been effectively sucked out of the stock. I'm perfectly happy being on the sidelines at the moment.

Craving more input? Start by adding PAREXEL International to your free and personalized watchlist so you can keep up with the latest news from the company.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.