For the current week, the overall ratings of three medical devices stocks are worse, according to the Portfolio Graderdatabase. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Given Imaging’s (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. In Portfolio Grader’s specific subcategory of Earnings Surprise, GIVN also gets an F. The stock’s trailing PE Ratio is 45.50. For more information, get Portfolio Grader’s complete analysis of GIVN stock.

Slipping from a C to a D rating, Greatbatch, Inc. (GB) takes a hit this week. 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 48.20. To get an in-depth look at GB, get Portfolio Grader’s complete analysis of GB stock.

Tornier NV’s (TRNX) rating falls this week to an F (“strong sell”), down from last week’s 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.