Quest Diagnostics Explained – Services, Testing, and Drug Screening Explained

Quest Diagnostics Incorporated (NYSE: DGX) is one of the largest clinical laboratory companies in the United States, providing diagnostic information services to patients, physicians, hospitals, employers, and government agencies. Headquartered in Secaucus, New Jersey, the company touches the lives of roughly one in three American adults every year and serves approximately half of U.S. physicians and hospitals. With nearly 56,000 employees, more than 2,000 patient service centers, and 2024 revenues of $9.87 billion, Quest operates at a scale that makes it a cornerstone of American healthcare diagnostics.

Company Background

Quest Diagnostics traces its origins to 1967, when pathologist Dr. Paul A. Brown founded Metropolitan Pathology Laboratory, Inc. in New Jersey—operating initially out of a small apartment with a $500 loan. The company was later renamed MetPath, Inc. and was acquired by Corning Glass Works in 1982. In 1996, Corning spun off its laboratory division as an independent publicly traded company under the name Quest Diagnostics.

Since then, Quest has grown substantially through a series of acquisitions, including SmithKline Beecham Clinical Laboratories in 1999, LabOne in 2005, and LifeLabs in Canada in 2024. The company completed eight acquisitions in 2024 alone, including four hospital outreach laboratory transactions, expanding its geographic reach and specialist testing capabilities.

Today, Quest processes specimens for approximately 550,000 patients on a typical workday, offering a test menu of thousands of options—from routine annual bloodwork to advanced genomic diagnostics.

Core Diagnostic Services

Quest Diagnostics is organized around two primary service areas: its core clinical laboratory business, which handles routine and specialty diagnostic testing, and a significant employer and occupational testing division focused on workplace wellness and drug screening.

Routine Clinical Testing

Quest’s routine testing menu covers the most frequently ordered diagnostics in primary care, including:

Specialty and Advanced Testing

Beyond routine diagnostics, Quest offers testing across more than a dozen clinical specialties, supported by a staff of approximately 900 physicians and Ph.D. scientists. Key specialty areas include:

Quest also operates QuestDirect, a consumer-initiated testing platform that allows patients to order health and wellness lab tests without a physician’s order.

Drug Testing at Quest Diagnostics: An Overview

Quest Diagnostics has a long-standing presence in workplace drug testing and describes itself as a leading provider of pre-employment drug screening for U.S. employers. The company has analyzed workforce drug testing data since 1988 and publishes the findings annually as the Drug Testing Index (DTI)—an industry-standard report based on the results of nearly 10 million workforce drug tests per year, released as a public service for employers, policymakers, and government agencies.

Quest’s drug testing laboratories hold three key certifications that apply to workplace testing programs:

The company maintains a combined network of nearly 10,000 collection sites across the United States, including company-owned patient service centers and preferred third-party locations. On-site and mobile collection services are also available for employers who need testing conducted at their facilities.

Types of Drug Tests Available

Quest offers several distinct specimen types for drug testing. The right choice depends on the detection window needed, the purpose of the test, and whether the program is federally regulated.

Urine Drug Testing

Urine testing is the most widely used method and the most flexible in terms of panel configuration. It is also the only specimen type approved for federally mandated testing programs, including Department of Transportation (DOT) testing for safety-sensitive transportation workers.

Quest describes urine testing as suitable for every standard workplace testing scenario: pre-employment, random, post-accident, reasonable suspicion, return-to-duty, and follow-up testing. The detection window for urine generally covers approximately 24 to 72 hours for most substances, though this varies considerably by drug, frequency of use, and individual metabolism.

Quest also offers rapid, point-of-collection testing (POCT) for urine—an instant on-site screen that provides preliminary results before a specimen is sent to a laboratory for confirmation.

Hair Drug Testing

Hair testing is the only method that provides up to a 90-day history of drug use. Because drugs and their metabolites are incorporated into the hair shaft from the bloodstream as hair grows, a sample of approximately 1.5 inches cut from close to the scalp covers roughly three months of potential exposure. A standard hair test requires approximately 100 to 120 strands of hair, collected under direct observation.

Hair testing is not accepted for federally mandated DOT programs but is widely used by non-DOT employers for pre-employment and random testing when a longer historical window matters. Quest notes that hair testing tends to produce a greater number of positives than urine testing due to its extended detection window.

Oral Fluid (Saliva) Drug Testing

Oral fluid testing collects a saliva specimen using a specialized device and is well suited to situations where very recent use is the concern. Quest states that oral fluid can detect most drugs starting soon after ingestion and extending out to approximately 24 to 48 hours after use—though for some drugs such as cocaine and heroin, the detection window may be shorter. Because collection is directly observed by default, oral fluid testing reduces the risk of specimen tampering.

Quest uses the Quantisal™ collection device, which features a volume indicator window to confirm that an adequate sample has been collected. Oral fluid testing is approved for use in federal workplace drug testing programs under HHS guidelines, making it an alternative to urine in those contexts. Initial screening is performed using enzyme immunoassay (EIA); non-negative results are confirmed by GC/MS or GC/MS/MS.

Breath Alcohol Testing

In addition to drug screening, Quest offers breath alcohol testing for employers who need to screen for alcohol use separately from drug panels. Non-negative DOT breath alcohol screens must be confirmed at a DOT-approved testing facility.

Drug Panels: Substances and Metabolites Tested

Drug tests detect metabolites—the chemical compounds the body produces as it processes a substance—rather than the drug itself. Quest offers a range of standard and expanded panels, from the five-drug federal standard to customized configurations covering additional substance classes.

Standard 5-Panel (DOT Compliance)

Required for federally regulated industries under DOT rules (transportation, aviation, pipeline, rail, and transit), the 5-panel covers:

Drug Class Primary Metabolite(s) Detected
Marijuana (cannabis) THC carboxylic acid (THC-COOH)
Cocaine Benzoylecgonine
Opiates Codeine, morphine, 6-acetylmorphine (6-AM)
Amphetamines Amphetamine, methamphetamine
Phencyclidine (PCP) PCP

Expanded Non-DOT Panels

Non-DOT employers can select broader panels. Quest offers 7-panel and 10-panel configurations, as well as fully customized options. The following additional drug classes are available:

Additional Drug Class Notes
Barbiturates Sedative-hypnotic medications
Benzodiazepines Anti-anxiety medications commonly subject to misuse
Methadone Synthetic opioid used medically and illicitly
Oxycodone Semi-synthetic opioid; detection includes oxymorphone
Propoxyphene Pain reliever class
MDMA (Ecstasy) and MDA Detected alongside or added to the amphetamine class
Synthetic cannabinoids “K2” or “Spice” compounds not detected by standard THC screens
Synthetic stimulants “Bath salts” and related compounds

Quest also offers a Medical Professional Panel designed for healthcare industry employers, screening for a broader range of prescription drugs that may be more accessible in clinical settings. A steroids panel is available for employers where performance-enhancing drug use is a concern.

Substances Tested by Hair

Quest’s standard hair test covers five drug classes: amphetamines (including methamphetamine and MDMA), opiates (codeine, morphine, and 6-acetylmorphine), cocaine and its metabolites, the marijuana metabolite (THC carboxylic acid), and PCP. Available add-ons include expanded opiates (hydromorphone, hydrocodone, oxymorphone, and oxycodone), fentanyl, and methadone.

Detection Windows by Specimen Type

Detection windows vary by substance, dose and frequency of use, individual metabolism, and the concentration thresholds applied by the testing program. The table below reflects general ranges as published by Quest Diagnostics.

Specimen Type Typical Detection Window
Oral fluid (saliva) 24–48 hours for most drugs; shorter for some substances
Urine Approximately 24–72 hours for most substances; longer for chronic users or drugs like THC
Hair Up to approximately 90 days

How the Drug Testing Process Works

All laboratory-based drug testing at Quest follows a standardized, documented chain-of-custody process designed to ensure specimen integrity and produce results that hold up in compliance proceedings.

  1. Authorization: An employer or authorized party orders a test. Employees or applicants are directed to a Quest patient service center or affiliated collection site, or a mobile collector comes on-site.
  2. Specimen Collection: A trained collector verifies the donor’s identity and collects the specimen using the applicable protocol. A Custody and Control Form (CCF) is completed and signed by both the collector and the donor. The specimen is sealed with tamper-evident labels in the donor’s presence, establishing the chain of custody.
  3. Laboratory Screening: The specimen is shipped to a SAMHSA-certified Quest laboratory. An initial immunoassay screen determines whether any substance is present at or above the applicable threshold concentration. The large majority of specimens screen negative and results are reported promptly.
  4. Confirmation Testing: Non-negative specimens proceed to confirmatory analysis. Quest uses gas chromatography/mass spectrometry (GC/MS) or GC/MS/MS to identify and quantify specific drug compounds with a high degree of chemical precision. A result is only finalized as positive if the confirmed concentration meets or exceeds the applicable cutoff level.
  5. Medical Review Officer (MRO) Review: For federally regulated programs—and many non-DOT programs as well—all non-negative results are reviewed by a licensed Medical Review Officer (MRO), a physician trained in substance abuse and toxicology interpretation. The MRO contacts the donor to determine whether a legitimate prescription or medical explanation accounts for the result before any final outcome is reported to the employer.
  6. Results Reporting: Verified results are delivered to the employer or designated representative through Quest’s secure electronic reporting system.

When Drug Testing Is Conducted

Quest’s drug testing services apply to the full range of standard workplace and clinical testing scenarios:

The Drug Testing Index: Tracking Workforce Drug Use

A distinctive aspect of Quest’s role in the drug testing industry is the annual Drug Testing Index (DTI), published as a public service since 1988. The report analyzes nearly 10 million de-identified workforce drug tests per year and tracks positivity rates by substance, specimen type, industry, and testing reason.

The 2024 DTI—covering 2023 test data—found that the overall drug positivity rate in the combined U.S. workforce held at 4.6%, the highest level in more than two decades. Marijuana remained the most commonly detected substance across all specimen types. The report also found a continued rise in post-accident marijuana positivity and a notable increase in attempts to adulterate or substitute urine specimens—described by Quest researchers as specimen validity concerns. Cocaine positivity in the general workforce increased 9.1% in 2023, while opiate and opioid positivity continued a multi-year downward trend.

The DTI is widely referenced by employers, occupational health professionals, and public health researchers as a reliable longitudinal dataset on workplace substance use trends.

Summary

Quest Diagnostics is one of the most extensive clinical laboratory networks in the United States, offering a broad menu of diagnostic services from routine preventive screenings to advanced genomic and molecular testing. Its workplace drug testing division is among the largest in the country, operating from SAMHSA-certified, CAP-accredited, and CLIA-certified laboratories with a nationwide collection site network.

Drug testing at Quest covers urine, hair, oral fluid, and breath alcohol specimen types, with panels ranging from the federally mandated 5-drug DOT standard to customized multi-substance configurations that can include synthetic cannabinoids, steroids, and prescription drug classes not included in basic panels. The testing process follows a documented chain of custody from collection through immunoassay screening, mass spectrometry confirmation, and MRO review before results are reported.

Employers designing a drug testing program, and individuals going through one, should consult their occupational health provider, a third-party administrator, or Quest’s employer solutions team for guidance specific to their industry, regulatory obligations, and program goals.