Frequently Asked Questions

Is drug testing accurate?

Absolutely. Most laboratories use a two-step process in which each urine sample is divided and a portion is tested using a relatively simple, inexpensive, and accurate test (using enzyme immunoassay technology). If the results of that test are positive, then a second test on a portion of the remaining specimen is conducted using a different chemical process. The second – or confirmation – test uses gas chromatography/mass spectrometry (GC/MS). Only if both portions of the divided specimen show up positive is it considered a positive result by the testing lab.

The accuracy of the initial drug screen, the immunoassay test, ranges between 92% – 98%. The accuracy of the GC/MS confirmatory test is virtually 100% from a scientific standpoint. With the use of this two-step process and professional, accredited laboratories to eliminate human error in the process, there should be no concern regarding the accuracy of drug tests.

What about “false positives”?

Most of the popular stories about what triggers a ‘false positive’ – such as what you eat or drink, what cosmetics you use, or what over-the-counter medicines you take – are based on misconceptions. They either:

  1. don’t show up at all;
  2. are not detected at sufficient levels; or
  3. are easily distinguishable in the laboratory.

Some employees have claimed that passive inhalation of marijuana smoke caused their positive test results. However, studies have shown that the exposure would have had to be so constant and prolonged, and in such a confined space, as to represent an absurd scenario. In addition, the GC/MS confirmation cutoff levels allow for these circumstances. The claim of passive inhalation triggering a positive test result is easily rejected.

Can a drug test be “beaten”?

Yes, but the odds are long and getting longer all the time. The science of drug testing has progressed significantly in recent years. Some of the procedures that have been instituted to determine intentional attempts at “beating” a drug screen are:

  • Chain of Custody procedures and specific protocols that track the specimen from the moment of collection through the processing and storage procedure;
  • Temperature strips, which assure the sample temperature falls within the acceptable range at the time of collection;
  • Integrity testing, to determine creatinine & specific gravity levels, which detect attempts to dilute the specimen;
  • Adulterant testing, developed to identify the use of nitrites and other adulterants as a means to disguise drugs in the collected sample.

An applicant tests positive for drugs and claims there must be a mistake. Should I send him for another drug test?

Under no circumstances should an applicant or employee be allowed to have a new specimen collected when they dispute a drug test result. If the Chain of Custody is intact, and the initial positive results were confirmed by GC/MS procedure, there is virtually no room for error. Keep this in mind: these tests are highly structured, federally regulated, sophisticated procedures conducted in a certified laboratory. Instead of recollection, there are other options available at this point: re-confirming the original specimen via GC/MS at Quest, transporting the specimen to another certified lab for confirmation testing, or utilizing the services of an MRO.

What happens to the specimen when someone tests positive?

When a specimen tests positive during the initial screen, it is automatically scheduled to be processed by a separate procedure (GC/MS) to confirm the presence of the drug in question. If this sample is confirmed positive, then the balance of the specimen is stored under strict laboratory procedures for future needs. It is held under refrigerated conditions for at least six months.

How long do drugs stay in an individual’s system?

Drugs do not typically remain in the body for very long. Often no more than 24 – 72 hours, depending on the frequency of use and the individual’s body functions. Marijuana is the exception, staying sometimes from several days to several weeks, again depending on the circumstances. However, through hair analysis, drugs are detectable up to 90 days after drug use.

Must I have a drug policy in place before I start drug testing?

Yes! You must also notify all current employees of the new policy and allow sufficient time for this new policy to be recognized throughout your company. Although you may start pre-employment testing as soon as a drug screening policy is in place, it is strongly recommended that there be a waiting period before asking current employees to submit to testing.

Should I fire an individual for having a positive result?

Every company has a different policy. Some find termination as the only answer for a positive drug screen, as drug use is an immediate breach of company policy. On the other hand, many companies now offer Employee Assistance Programs (EAP), which include drug and alcohol counseling and treatment. An EAP can be funded by the company or require the employee to fund their own treatment, as long as they can pass subsequent drug screens. Whatever procedure you adopt, the final determination will be the consistency by which you implement your discipline. Some states now require an EAP as part of the company’s drug testing policy. Check your state laws for clarification.

We do pre-employment drug screening. Is it important for my company to do other types of drug testing?

Absolutely. Pre-employment urine screening is only effective in discovering hard-core abusers; those who cannot abstain for a short period of time while they look for work. The only effective way to truly make your place of employment drug-free is to include in your drug policy the stipulation that you reserve the right to test for a variety of recognized specific situations, such as random selection, reasonable suspicion, post-accident or return to duty. Be aware that some states limit or forbid the use of certain types of drug screening.

I’ve heard about hair testing. Is this something we should consider?

Hair testing is gaining more acceptance for pre-employment screening because of the lengthy detection period. However, it is more expensive. It is also not appropriate for post-accident or for-cause screening, as the hair must grow out at least a week before drugs can be detected. Therefore your drug screening policy should stipulate you reserve the right to use either method of drug testing.

What is a Chain of Custody and why is it important?

This is the detailed documentation of the drug screening process. It accounts for the integrity of each step of the procedure by tracking the handling and storage of the specimen from collection to disposal. This multi-part medical document, with assigned bar-coded numbers, facilitates the process and documents by whom, when and for what purpose the specimen was handled. Clinical labs will not proceed with a drug screen if they recognize the chain of custody has been broken. With a fully executed Chain of Custody, the drug screen result is completely and legally defensible.

Does the lab handle a DOT specimen differently than a non-DOT one?

The Department of Transportation has very strict guidelines for collection sites and labs in regards to the collection and testing of drug test specimens. However, Quest uses the same procedures and technology to test ALL specimens, regardless of whether the donor is DOT regulated. All specimens are processed with the same screening and confirmation technology. The biggest differences lie in the collection requirements; for example, DOT tests are collected as split specimens.What is the difference between a 5-panel screen and a 10-panel screen?The collection procedure and screening process are identical. The difference is the number of drugs for which the specimen is screened. All DOT tests legally require a 5 panel screen, while non-DOT tests may utilize any size panel. Hire Level’s default screen is a 12-panel.

What is GC/MS and why is this important?

Gas Chromatography / Mass Spectrometry (GC/MS) is the superior and highly accurate drug confirmation test that is used on initial positive results.

What is an adulterated specimen and do you screen for that?

Adulteration screening is standard in our drug screens. It screens for the presences of nitrites, a chemical purchased for the distinct purpose of adulterating the specimen to obscure the presence of drugs. Although it might be successful in obscuring drugs, the nitrites themselves are detectable and can be considered a positive drug screen; and therefore employment decisions can be made based on that confirmed positive. Nitrites are not a personality-altering substance, nor addictive.

What is the difference between a diluted specimen, a substituted specimen and anadulterated specimen?

‘Dilute’ indicates that a specimen is below minimum concentrate levels, and therefore the results are inconclusive. If a specimen is sufficiently diluted, it makes it difficult for the lab to identify any drugs that might be present. Specifically, a diluted specimen has a creatinine reading less than 20 mg/dL, but greater than 5 mg/dL, and a specific gravity less than 1.003, but greater than 1.001. A diluted specimen may be the result of a medical condition, increased ingestion of fluid, or the addition of a liquid to the collected specimen in order to decrease the concentration. There is no way to determine if the dilution was intentional or not.

A substituted specimen is when something other than human urine has been submitted as the candidate’s collected sample. Simply stated, such specimens do not exhibit the clinical signs or characteristic associated with normal urine. Specifically, a substituted specimen has a creatinine of less than or equal to 5mg/dL and a specific gravity less than or equal to 1.001 or greater than or equal to 1.020.

An adulterated specimen is when an individual has introduced a foreign substance into the collected sample to intentionally disguise drugs in the urine. There are numerous products on the market, such as Klear, that are very easily bought on the internet and have been designed for just this purpose. Specifically, an adulterated specimen is when the nitrite concentration is equal to or great than 500 cg/mL.

Quest Diagnostics has the ability to distinguish, measure and report all of these attempts to beat a drug screen. In the case of a diluted specimen, we do recommend a re-collection only if the first results were negative. Do not, however, give the individual any advance warning – you don’t want to give them sufficient time to ingest a lot of fluids again. In the case of a substituted or adulterated result, you may consider the results to be a positive drug screen and make employment decisions on that conclusion.

What are ‘cut-off levels’?

A cut-off level is the value that denotes the threshold for determining at what point there is a sufficient amount of a drug to be considered a positive result. It is possible to have a trace amount of a drug in the specimen and not test positive because the cut-offs are designed to pinpoint drug abusers and not, for instance, second hand inhalation.

What is a split sample?

Split sampling is when a specimen is divided at the time of collection and maintained as two separate samples. DOT regulations and some states require split sampling as standard procedure. However, in the case of an initial positive and absence of a split sample, the clinical lab is required to automatically retain the balance of the initial specimen for a confirmation test, as well as future requirements, for up to six months.

What is the difference between laboratories?

There can be a multitude of differences, but the most important is whether or not it is a certified lab. While not required in the private sector, it is highly advisable and more defensible in terms of a legal standpoint to use a certified laboratory. Drug testing laboratories can be certified by:

  • US Dept of Health and Human Services (HHA) Substance Abuse & Mental Health Services Administration (SAMHSA);
  • College of American Pathology; and
  • State health departments.

Quest Diagnostics is certified by SAMHSA, the College of American Pathology, and all other states, where required.

What are NIDA and SAMHSA?

SAMHSA stands for Substance Abuse & Mental Health Services Administration. NIDA stands for National Institute for Drug Abuse. These are federal bureaus that create and administer public policies and standards where drug and alcohol issues are involved. The cutoff levels for drug screening are set by SAMHSA, and only laboratories that meet SAMHSA certification requirements are utilized by Hire Level.

Where do I find the special requirement and laws for each state concerning drug screening?

Your state bar association can lead you to many publications and sources that will answer this need. You might also want to contact the Institute for a Drug-Free Workplace, which offers many publications dealing with state and federal drug testing laws, as well as many other drug testing topics. Their website address is