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’s (NASDAQ:GIVN) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. 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. Shares of the stock have been trading at an exceptionally rapid pace, up threefold from the week prior. The stock has a trailing PE Ratio of 37.40. To get an in-depth look at GIVN, get Portfolio Grader’s complete analysis of GIVN stock.

Greatbatch, Inc. (NYSE:GB) experiences a ratings drop this week, going from last week’s 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 507.70. For a full analysis of GB stock, visit Portfolio Grader.

Tornier NV (NASDAQ:TRNX) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Tornier designs, outsources the manufacture of and markets orthopedic products. The stock gets F’s in Earnings Momentum and Earnings Revisions. For more information, get Portfolio Grader’s complete analysis of TRNX stock.

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.