This week, the ratings of three Medical Devices stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Given Imaging (NASDAQ:GIVN) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Given Imaging has developed a proprietary wireless imaging system that allows a medical professional to examine the gastrointestinal tract. GIVN also rates an F in Portfolio Grader’s specific subcategory of Earnings Surprise. The stock price has dropped 11.1% over the past month, worse than the 1.8% increase the Nasdaq has seen over the same period of time. The stock has a trailing PE Ratio of 35.10. To get an in-depth look at GIVN, get Portfolio Grader’s complete analysis of GIVN stock.

The rating of Greatbatch (NYSE:GB) declines this week from a C to a D. Greatbatch develops and manufactures power sources, feedthroughs, and wet tantalum capacitors used in implantable medical devices. The stock gets F’s in Earnings Growth, Earnings Momentum, and Margin Growth.

For more information, get Portfolio Grader’s complete analysis of GB stock.

Tornier (NASDAQ:TRNX) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Tornier designs, outsources the manufacture of and markets orthopedic products. The stock gets F’s in Earnings Momentum and Earnings Revisions. Wall Street appears to agree with the stock downgrade, with share prices dropping 6.8% over the past month. For a full analysis of TRNX stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.