This week, 4 Life Sciences Tools & Services stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Waters Corporation (WAT) boosts its rating from a B to a A this week. Waters Corporation is an analytical instrument manufacturer that designs, manufactures, sells and services liquid chromatography, ultra performance liquid chromatography, mass spectrometry instrument systems, and support products. The company also gets A’s in return on equity. For more information, get Portfolio Grader’s complete analysis of WAT stock.

This week, NanoString Technologies, Inc. (NSTG) pushes up from a C to a B rating. The company also gets A’s in sales growth and earnings revisions. For more information, get Portfolio Grader’s complete analysis of NSTG stock.

Compugen Ltd. (CGEN) is seeing ratings go up from a C last week to a B this week. Compugen Ltd. focuses on the therapeutic proteins and monoclonal antibodies to address unmet needs in the fields of immunology and oncology. The company also gets A’s in sales growth, earnings revisions, and earnings surprise. For more information, get Portfolio Grader’s complete analysis of CGEN stock.

Sequenom, Inc.’s (SQNM) ratings are looking better this week, moving up to a B from last week’s C. Sequenom, Inc. is a molecular diagnostic testing and genetics analysis company. The company also gets A’s in earnings surprise. For more information, get Portfolio Grader’s complete analysis of SQNM 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.