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”).

Given Imaging (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. Trade volume fell markedly in the past week, standing at half of the previous rate. The stock has a trailing PE Ratio of 58.10. For a full analysis of GIVN stock, visit Portfolio Grader.

Greatbatch, Inc. (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’s trailing PE Ratio is 46.50. To get an in-depth look at GB, get Portfolio Grader’s complete analysis of GB stock.

Tornier NV (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. 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.