[18] The purchase of SmithKline Beecham also included the lab's medical sample transport airline (ICAO: LBQ, call sign: LABQUEST) originally founded in 1988.

[21] In response to Mohapatra's resignation after eight years with Quest, former Philips Healthcare CEO Stephen Rusckowski was appointed.

[23] In 2016, Quest collaborated with Safeway to bring testing services to twelve of its stores in California, Maryland, Virginia, Texas and Colorado.

[33] Quest Diagnostics set a record in April 2009 when it paid $302 million to the government to settle a Medicare fraud case alleging the company sold faulty medical testing kits.

It was the largest qui tam (whistleblower) settlement paid by a medical lab for manufacturing and distributing a faulty product.

[51] In May 2011, Quest paid $241 million to the state of California to settle a False Claims Act case that alleged the company had overcharged Medi-Cal, the state's Medicaid program, and provided illegal kickbacks as incentives for healthcare providers to use Quest labs.

[52] In 2018, Quest Diagnostics was among a number of US based labs linked to inaccuracies of over 200 women's cervical smear tests for CervicalCheck, Ireland's national screening program.

[53][54] Audits of the testing performed by Quest (and another subcontractor Clinical Pathology Laboratories, Inc. of Austin Texas) showed a high rate of errors in analysis of samples which led to lawsuits[55] and a government inquiry.