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

VWR Corp. (VWR) boosts its rating from a C to a B this week. The company also gets A’s in operating margin growth and free cash flow. For more information, get Portfolio Grader’s complete analysis of VWR stock.

Accelerate Diagnostics, Inc. (AXDX) shows solid improvement this week. The company’s rating rises from a C to a B. Accelerate Diagnostics, Inc. develops diagnostic systems for bacterial infections. The company also gets A’s in sales growth and earnings revisions. For more information, get Portfolio Grader’s complete analysis of AXDX stock.

Nanostring Technologies, Inc.’s (NSTG) ratings are looking better this week, moving up to a B from last week’s C. The company also gets A’s in sales growth, earnings revisions, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of NSTG stock.

Enzo Biochem, Inc. (ENZ) is seeing ratings go up from a C last week to a B this week. Enzo Biochem, Inc. researches, develops, and manufactures health care products based on molecular biology and genetic engineering techniques. The company also gets A’s in earnings revisions and earnings momentum. For more information, get Portfolio Grader’s complete analysis of ENZ 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.