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

Sequenom, Inc.’s (SQNM) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Sequenom is a molecular diagnostic testing and genetics analysis company. SQNM also rates an F in Portfolio Grader’s specific subcategory of Cash Flow. The stock price has dropped 16.2% over the past month, worse than the 1.3% decrease the Nasdaq has seen over the same period of time. As of Feb. 20, 2014, 18.6% of outstanding Sequenom, Inc. shares were held short. For a full analysis of SQNM stock, visit Portfolio Grader.

QIAGEN NV (QGEN) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Qiagen provides sample and assay technologies. Share prices fell 8.1% over the past month. The trailing PE Ratio for the stock is 81.40. For more information, get Portfolio Grader’s complete analysis of QGEN stock.

This week, BG Medicin (BGMD) drops from a C to a D rating. BG Medicine is a life sciences company focused on the discovery, development and commercialization of novel diagnostic tests based on biomarkers for high-value market opportunities in healthcare that it identifies. The stock gets F’s in Equity, Cash Flow and Sales Growth. Shares of the stock have been changing hands at an unusually rapid pace, four times the rate of the week prior. To get an in-depth look at BGMD, get Portfolio Grader’s complete analysis of BGMD 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.