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

This week, Enzo Biochem, Inc. (ENZ) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Enzo Biochem researches, develops, and manufactures health care products based on molecular biology and genetic engineering techniques. In Portfolio Grader’s specific subcategory of Equity, ENZ also gets an F. Shares of the stock have been exchanging at an usually rapid pace, twice the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of ENZ stock.

Slipping from a C to a D rating, BG Medicin (BGMD) takes a hit this week. BG Medicine develops and markets diagnostic tests. The stock gets F’s in Equity, Cash Flow and Sales Growth. To get an in-depth look at BGMD, get Portfolio Grader’s complete analysis of BGMD stock.

This is a rough week for Luminex Corporation (LMNX). The company’s rating falls to D from the previous week’s C. Luminex develops, manufactures and markets biological testing technologies with applications throughout the clinical diagnostic and life science industries. The stock also gets an F in Earnings Revisions. For more information, get Portfolio Grader’s complete analysis of LMNX 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.