Bloomberg News
Steve Rusckowski

Quest Diagnostics (DGX - Get Report) shares posted a healthy increase Tuesday after the medical-testing firm passed its quarterly financial checkup with flying colors.

The stock rose 4.6% to $102.56 after the Secaucus, N.J. company, which does everything from drug screening to gene-based and molecular testing, beat analyst estimates for second-quarter earnings, revenue and operating margin.

Quest earned an adjusted $1.73 a share from continuing operations, beating the $1.68 estimate of analysts surveyed by FactSet.

Revenue came in at $1.95 billion, up 1.8% from $1.92 billion in the year-earlier period. Analysts were looking for $1.94 billion.

Steve Rusckowski, Quest's chairman, president and CEO, cited expanded network access for the stronger-than-expected results.

A big boost for Quest has been the firm's "new Preferred Lab Network status within UnitedHealthcare (UNH - Get Report) , which represents a multiyear opportunity that will build over time," Rusckowski said in a statement.

Strong volume growth "combined with our strategy to drive operational excellence helped offset the significant reimbursement pressures we are experiencing this year."