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 Affymetrix (NASDAQ:AFFX), a maker of life science tools and molecular diagnostic products, sank as much as 15% after announcing its preliminary first-quarter revenue results.

So what: For the quarter, Affymetrix anticipates reporting $78 million in revenue -- of which $19 million will be from its eBioscience segment, which it acquired in June -- and should have approximately $38 million in cash on hand when the quarter ends. Wall Street had been forecasting revenue of $83.3 million for the first quarter. Affymetrix's CEO, Frank Witney, blamed weakness on its gene expression business around the globe, but singled out Japan as the most disappointing region. Witney also reaffirmed the company's commitment to paying down its remaining $70 million in debt.

Now what: It's kind of hard to get excited about eBioscience's contribution, Affymetrix's shrinking debt, or its recent genotyping deal with BioBank, when Witney noted that weakness was seen around the globe. That right there is a cue that this isn't a one-quarter problem, but could represent a genuine slowdown in diagnostic demand altogether -- especially abroad. As much as I like the concept of molecular diagnostic testing, even going so far as to say it could benefit from the implementation of the Patient Protection and Affordable Care Act, I'd suggest keeping your distance from Affymetrix until its results show at least some signs of improvement.

Craving more input? Start by adding Affymetrix to your free and personalized Watchlist so you can keep up on the latest news with 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.

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