The ratings of three life science stocks are down this week, according to the Portfolio Grader database. 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. For Portfolio Grader’s specific subcategory of Equity, ENZ also gets an F. Shares of the stock are changing hands at twice the rate they were a week ago. For more information, get Portfolio Grader’s complete analysis of ENZ stock.

The rating of BG Medicin (BGMD) declines this week from a C to a D. 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.

Luminex Corporation (LMNX) experiences a ratings drop this week, going from last week’s C to a D. 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.