Editor's Note: TheStreet ratings do not represent the views of TheStreet's staff or its contributors. Ratings are established by computer based on metrics for performance (which includes growth, stock performance, efficiency and valuation) and risk (volatility and solvency). Companies with poor cash flow or high debt levels tend to earn lower ratings in our model All three major indices are trading down today with the Dow Jones Industrial Average ( ^DJI) trading down 6 points (0.0%) at 14,695 as of Friday, April 26, 2013, 12:50 PM ET. The NYSE advances/declines ratio sits at 953 issues advancing vs. 1,941 declining with 134 unchanged. The Health Care sector currently sits down 0.38 versus the S&P 500, which is down 0.43. On the negative front, top decliners within the sector include Covidien ( COV), down 6.58, Agilent Technologies ( A), down 4.40, Vertex Pharmaceuticals ( VRTX), down 1.74, WellPoint ( WLP), down 1.64 and Medtronic ( MDT), down 1.36. Top gainers within the sector include Celgene Corporation ( CELG), up 1.5%, Teva Pharmaceutical Industries ( TEVA), up 0.7% and Gilead ( GILD), up 0.7%. TheStreet Ratings group would like to highlight 3 stocks pushing the sector lower today: 3. PerkinElmer ( PKI) is one of the companies pushing the Health Care sector lower today. As of noon trading, PerkinElmer is down $4.28 (-12.4%) to $30.19 on heavy volume Thus far, 6.9 million shares of PerkinElmer exchanged hands as compared to its average daily volume of 1.0 million shares. The stock has ranged in price between $29.50-$31.11 after having opened the day at $29.62 as compared to the previous trading day's close of $34.47. PerkinElmer, Inc. provides products, services, and solutions to the diagnostics, research, environmental, industrial, and laboratory services markets worldwide. The company operates in two segments, Human Health and Environmental Health. PerkinElmer has a market cap of $3.8 billion and is part of the health services industry. The company has a P/E ratio of 56.5, above the S&P 500 P/E ratio of 17.7. Shares are up 8.6% year to date as of the close of trading on Thursday. TheStreet Ratings rates PerkinElmer as a buy. The company's strengths can be seen in multiple areas, such as its solid stock price performance, growth in earnings per share, compelling growth in net income, revenue growth and largely solid financial position with reasonable debt levels by most measures. We feel these strengths outweigh the fact that the company shows weak operating cash flow. Get the full PerkinElmer Ratings Report now. Exclusive Offer: Jim Cramer's 'go-to' small/mid-cap guru Bryan Ashenberg only buys stocks he thinks could return 50-100%. See his top picks for 14-days FREE.