Editing Drug test (section)

==Methodologies==
Before testing samples, the [[tamper-evident]] seal is checked for integrity. If it appears to have been tampered with or damaged, the laboratory rejects the sample and does not test it.

Next, the sample must be made testable. Urine and oral fluid can be used "as is" for some tests, but other tests require the drugs to be extracted from urine. Strands of hair, patches, and blood must be prepared before testing. Hair is washed in order to eliminate second-hand sources of drugs on the surface of the hair, then the [[keratin]] is broken down using [[enzymes]]. [[Blood plasma]] may need to be separated by [[centrifuge]] from [[blood cells]] prior to testing. Sweat patches are opened and the sweat collection component is removed and soaked in a [[solvent]] to dissolve any drugs present.

Laboratory-based drug testing is done in two steps. The first step is the '''screening test''', which is an immunoassay based test applied to all samples. The second step, known as the confirmation test, is usually undertaken by a laboratory using highly specific chromatographic techniques and only applied to samples that test positive during the screening test.<ref name="principles of drug testing technology">[http://www.drugtestsdirect.com.au/docs/other/principles-of-drug-testing-technology.pdf "Principles of Drug Testing Technology,"] {{Webarchive|url=https://web.archive.org/web/20130419032353/http://www.drugtestsdirect.com.au/docs/other/principles-of-drug-testing-technology.pdf |date=April 19, 2013 }}</ref> Screening tests are usually done by [[immunoassay]] ([[Enzyme Multiplied Immunoassay Technique|EMIT]], [[ELISA]], and RIA are the most common). A "[[wikt:dipstick|dipstick]]" drug testing method which could provide screening test capabilities to field investigators has been developed at the [[University of Illinois at Urbana–Champaign|University of Illinois]].<ref>{{cite news |author=Jim Barlow |title=A Little Dab Will Do It |url=http://www.las.uiuc.edu/news/2006fall/06nov_dipstick.html |work=LASNews |publisher=University of Illinois |date=November 2006 |access-date=November 29, 2006 |archive-url=https://web.archive.org/web/20070129082943/http://www.las.uiuc.edu/news/2006fall/06nov_dipstick.html |archive-date=January 29, 2007 |url-status=dead |df=mdy}}</ref>

After a suspected positive sample is detected during screening, the sample is tested using a '''confirmation test'''. Samples that are negative on the screening test are discarded and reported as negative. The confirmation test in most laboratories (and all [[SAMHSA]] certified labs) is performed using [[mass spectrometry]], and is precise but expensive. False positive samples from the screening test will almost always be negative on the confirmation test. Samples testing positive during both screening and confirmation tests are reported as positive to the entity that ordered the test. Most laboratories save positive samples for some period of months or years in the event of a disputed result or lawsuit. For workplace drug testing, a positive result is generally not confirmed without a review by a Medical Review Officer who will normally interview the subject of the drug test.

===Urine drug testing===
Urine drug test kits are available as on-site tests, or laboratory analysis. Urinalysis is the most common test type and used by federally mandated drug testing programs and is considered the Gold Standard of drug testing. Urine based tests have been upheld in most courts for more than 30 years. However, urinalysis conducted by the Department of Defense has been challenged for reliability of testing the metabolite of cocaine. There are two associated metabolites of cocaine, benzoylecgonine (BZ) and ecgonine methyl ester (EME), the first (BZ) is created by the presence of cocaine in an aqueous solution with a pH greater than 7.0, while the second (EME) results from the actual human metabolic process. The presence of EME confirms actual ingestion of cocaine by a human being, while the presence of BZ is indicative only. BZ without EME is evidence of sample contamination, however, the US Department of Defense has chosen not to test for EME in its urinalysis program.<ref>{{cite news |url=https://www.independent.co.uk/arts-entertainment/books/features/books-of-the-year-2013-sport-8973040.html | location=London | work=The Independent | first=Chris | last=Maume | title=Books of the year 2013: Sport | date=November 29, 2013 | access-date=August 26, 2017 | archive-date=December 20, 2016 | archive-url=https://web.archive.org/web/20161220064035/http://www.independent.co.uk/arts-entertainment/books/features/books-of-the-year-2013-sport-8973040.html | url-status=live }}</ref>{{relevance inline|date=October 2016}}

A number of different analyses (defined as the unknown substance being tested for) are available on Urine Drug Screens.

===Spray drug testing===
Spray (sweat) drug test kits are non-invasive. It is a simple process to collect the required specimen, no bathroom is needed, no laboratory is required for analysis, and the tests themselves are difficult to manipulate and relatively tamper-resistant. The detection window is long and can detect recent drug use within several hours.

There are also some disadvantages to spray or sweat testing. There is not much variety in these drug tests, only a limited number of drugs can be detected, prices tend to be higher, and inconclusive results can be produced by variations in sweat production rates in donors.  They also have a relatively long specimen collection period and are more vulnerable to contamination than other common forms of testing.<ref name="Drug Test"/>

===Hair drug testing===
Hair drug testing is a method that can detect drug use over a much longer period of time than saliva, sweat or urine tests. Hair testing is also more robust with respect to tampering. Thus, hair sampling is preferred by the US military<ref name=idk38>{{Cite thesis|last=Hatala|first=John W.|date=June 2003|title=The Feasibility of Testing Hair for Illicit Drug Use in the United States Marine Corps|place=Monterey, California|publisher=[[Naval Postgraduate School]]|pages=2|url=http://www.usna.edu/IR/htmls/lead/database/cohort6/c06_hatala.pdf|access-date=May 7, 2009|hdl=10945/976|hdl-access=free|archive-date=January 17, 2009|archive-url=https://web.archive.org/web/20090117085241/http://www.usna.edu/IR/htmls/lead/database/cohort6/c06_hatala.pdf|url-status=live}}</ref> and by many large corporations, which are subject to [[Drug-Free Workplace Act of 1988]].

Head hair normally growth at the rate of 0.5&nbsp;inches per month.<ref name="zme">{{cite web |url=https://www.zmescience.com/other/science-abc/how-fast-hair-grows-042394/ |title=How fast hair grows, and other hairy science |last=Puiu |first=Tibi |date=August 23, 2018 |website=zmescience.com |publisher=ZME Science |access-date=September 28, 2018 |quote=The hair on your head grows about 6 inches a year. |archive-date=August 30, 2018 |archive-url=https://web.archive.org/web/20180830142322/https://www.zmescience.com/other/science-abc/how-fast-hair-grows-042394/ |url-status=live }}</ref> Thus, the most common hair sample length of 1.5" from the scalp would detect drug use within the last 90-100 days. 80-120 strands of hair are sufficient for the test.<ref name="i910">{{cite book | title=Analytical and Practical Aspects of Drug Testing in Hair | publisher=CRC Press | date=2006-08-30 | isbn=978-0-429-24525-1 | doi=10.1201/9781420006193 | page= | editor-last1=Kintz | editor-first1=Pascal }}</ref> In the absence of hair on the head, body hair can be used as an acceptable substitute. This includes facial hair, the underarms, arms, and legs or even pubic hair. Because body hair usually grows slower than head hair, drugs can often be detected in body hair for longer periods, e.g. up to 12 months. Currently, most entities that use hair testing have prescribed consequences for individuals removing hair to avoid a hair drug test.

Most drugs are analysed in hair samples not as the original psychoactive molecules, but rather as their metabolytes. For example, [[ethanol]] is determined as [[ethyl glucuronide]], while [[cocaine]] use is confirmed using [[ecgonine]]. Testing for metabolytes reduces the likelihood of false positive results due to contamination. One disadvantage of hair testing is, that it cannot detect recent drug use, because it takes at least a week after a drug intake for the metabolytes to show up in a growing hair above the skin.<ref name=idk38/> Urine tests are better suited for detecting recent (within a week) drug use.

In a practical test, hair sample is usually washed with a low polarity solvent (such as [[dichloromethane]]) to remove surface contaminations. Then, the sample is pulverized and extracted with a more polar solvent, such as methanol.<ref name="h623">{{cite journal | last1=Musiał | first1=Jadwiga | last2=Powierska-Czarny | first2=Jolanta | last3=Czarny | first3=Jakub | last4=Raczkowski | first4=Michał | last5=Galant | first5=Natalia | last6=Buszewski | first6=Bogusław | last7=Gadzała-Kopciuch | first7=Renata | title=One-step extraction and determination of 513 psychoactive substances, drugs, and their metabolites from hair by LC–MS/MS | journal=Archives of Toxicology | volume=96 | issue=11 | date=2022 | issn=0340-5761 | pmid=36008489 | pmc=9525419 | doi=10.1007/s00204-022-03343-w | pages=2927–2933| bibcode=2022ArTox..96.2927M }}</ref>

Although thousand different substances can be determined in a single [[gas chromatography–mass spectrometry]] or [[liquid chromatography–mass spectrometry]] experiment, due to the low concentration of analytes, practical measurements (see [[Gas chromatography%E2%80%93mass spectrometry#Selective ion monitoring|selective ion monitoring]]) are limited to a smaller number (10-20) of analytes. [[Designer drugs]] are usually missed in such measurements, because the analyst must know in advance what chemicals to look for.

Most hair testing laboratories use the aforementioned [[chromato-mass-spectrometry]] methods for confirmation or for rarely tested drugs only. Mass screening (preliminary or final) is usually done with [[immunoassays]], because of their lower cost.