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 NxStage Medical (NASDAQ:NXTM), a medical device maker that focuses on treating diseases of the kidney, slumped as much as 19% after reporting disappointing third-quarter earnings results.

So what: For the quarter, NxStage Medical delivered a 9% increase in revenue to $66.9 million as adoption of its NxStage System One improved. Modest gains were witnessed in all operational segments, including at-home, critical care, and in-center care. Net loss, however, nearly doubled to $5 million, or an adjusted $0.08 per share, from $2.6 million, or $0.04 per share, in the year-ago period. By comparison, Wall Street anticipated a narrower loss of $0.06 and about $66.8 million in revenue.

Looking ahead, though, is where the wheels fell off the wagon. NxStage sees fourth-quarter revenue of $67 million to $68.5 million with an adjusted EPS loss of $0.08-$0.10. The current consensus called for a loss of just $0.05 per share on $71.5 million in revenue. The reason for the weaker guidance, according to Matthew Towse, NxStage's chief financial officer, is due to a lower ramp up of international sales and weaker domestic critical care sale expectations.

Now what: Here we are once again with a company that looks like an attractive buy on paper, but that's failing to deliver the goods to shareholders on a consistent basis. With 25.3 million people in this country currently having diabetes, and diabetes being a leading cause of kidney problems, I can only assume that as baby boomers age NxStage is going to see a tremendous surge in demand for its devices. In the interim, though, NxStage is going to continue to disappoint investors until it can pare its losses and return to high single-digit growth or better. With that in mind I'm perfectly happy adding NxStage Medical to my watchlist, but I'd suggest waiting for growth to reaccelerate before considering an investment here.