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

This week, Given Imaging (NASDAQ:GIVN) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Given Imaging has developed a proprietary wireless imaging system that allows a medical professional to examine the gastrointestinal tract. In Portfolio Grader’s specific subcategory of Earnings Surprise, GIVN also gets an F. The trailing PE Ratio for the stock is 42.30. To get an in-depth look at GIVN, get Portfolio Grader’s complete analysis of GIVN stock.

Greatbatch, Inc. (NYSE:GB) is having a tough week. The company’s rating falls 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. The stock currently has a trailing PE Ratio of 44.00. For more information, get Portfolio Grader’s complete analysis of GB stock.

Tornier NV (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. The stock price has dropped 24.6% over the past month, worse than the 1.3% decrease the Nasdaq has seen over the same period of time. 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.