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 UnitedHealth Group Incorporated 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."