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

Derma Sciences, Inc. (DSCI) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Derma Sciences markets and sells a range of skin care, wound management, and specialty securement devices. In Portfolio Grader’s specific subcategories of Equity, Cash Flow and Sales Growth, DSCI also gets an F. Shares of the stock have been changing hands at an unusually rapid pace, three times the rate of the week prior. To get an in-depth look at DSCI, get Portfolio Grader’s complete analysis of DSCI stock.

St. Jude Medical, Inc.’s (STJ) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. St. Jude Medical makes and distributes cardiovascular medical devices. For more information, get Portfolio Grader’s complete analysis of STJ stock.

This is a rough week for Baxter International (BAX). The company’s rating falls to D from the previous week’s C. Baxter International develops, manufactures and markets products related to hemophilia, immune disorders, infectious diseases, kidney disease, trauma, and other chronic and acute medical conditions. The stock also gets an F in Earnings Revisions. To get an in-depth look at BAX, get Portfolio Grader’s complete analysis of BAX stock.

This week, Zimmer Biomet Holdings, Inc.’s (ZBH) rating worsens to a D from the company’s C rating a week ago. The stock gets F’s in Earnings Growth, Earnings Momentum and Margin Growth. The trailing PE Ratio for the stock is 51.60. For more information, get Portfolio Grader’s complete analysis of ZBH 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.