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 research company Covance (UNKNOWN:CVD.DL) have leapt more than 25% Monday after agreeing to be acquired by Laboratory Corp. of America (NYSE:LH) for $6.1 billion in cash and stock.

So what: LabCorp will pay $105.12 for each Covance share -- a 4.9 % premium over the stock's current price of roughly $100.25 -- with $75.76 of the purchase price paid in cash and the balance paid in LabCorp shares, which would make Covance shareholders owners of approximately 16% of LabCorp, according to news reports. The deal includes LabCorp's assumption of roughly $500 million in Covance debt, and each Covance share will be converted into 0.2686 LabCorp shares after the cash payment.

Now what: Prior to the deal, LabCorp and Covance shares had produced almost exactly the same return over the past five years, with Covance gaining 51.2% to LabCorp's gain of 56%. Both results trail the S&P's near-doubling over the same time frame, and LabCorp's 8% drop on the deal indicates that its current shareholders aren't too keen on the tie-up. If you were waiting for a good time to get out of Covance, you've got it today.