Drug Testing Toxicology
|
· GC/MS and initial cutoff levels |
|
|
|
|
GC/MS Confirmation testing and drug detection cutoff levels
Varian, Inc., a producer and marketer of products for abused drug testing, strongly supports the FDA requirement (see box) regarding confirmation of in vitro drug testing products manufactured for the initial testing of drugs of abuse. The information contained herein is intended to assist our customers as they develop or assess their own drug testing policies.
All of our rapid drugs of abuse testing (DAT) products and other immunoassays provide only a preliminary analytical result. A more specific alternate chemical method must be used in order to obtain a confirmed analytical result. Gas chromatography/mass spectrometry (GC/MS) is the preferred confirmatory method. Clinical consideration and professional judgment should be applied to any drug of abuse test result, particularly when preliminary positive results are used. |
A preliminary test is a single test result based on an OnTrak? product when it is used as an initial screen.
A confirmation test is a second test which offers a more specific chemical method for the detection of the desired substance. The preferred confirmation method is Gas Chromatography/Mass Spectrometry (GC/MS).
|
OnTrak TesTcup? alone = Preliminary result
OnTrak TesTcup plus GC/MS = Confirmed result |
Confirmation testing is the second step of testing following the detection of a positive result on the preliminary or screening test.
The purpose of confirmation is to eliminate any false positive results that may have originated from an initial screening process. To eliminate false positive test results, a confirmation test that is highly specific and possibly more sensitive should be used. It is important to note that confirmation testing is not the same as repeat testing in that running the same test a second time does not eliminate systematic errors. More specific confirmation tests used to identify drugs of abuse are generally thought to be of three types:
- Gas liquid chromatography (GC)
- High performance liquid chromatography (HPLC)
- Gas chromatography with mass spectrometry (GC/MS)
All three of these methods are both highly specific and sensitive to small quantities of the particular drug being tested. GC/MS is the most specific and sensitive of the three methods. Consistent with FDA position, Varian, Inc. strongly recommends confirmation testing using GC/MS in situations requiring a confirmed analytical result.
Substance Abuse and Mental Health Services Administration (SAMHSA, formerly NIDA) Mandatory Guidelines for Federal Workplace Drug Testing Programs
Drug testing may be conducted for a wide variety of reasons such as a condition for employment, eligibility for probation, parole, or work release, or even to participate in athletic events. It is obvious that in certain situations an incorrect result could negatively impact an individual. When run according to the package insert, the OnTrak products produce results with a very high degree of accuracy. Though our tests produce accurate results, there may be instances where a false positive result may be encountered. These may be due to administration / human error such as mislabeling, incorrect logging or recording, or product mishandling. Also with all immunoassays there are a small number of potential cross-reacting substances. By far the most common is in the amphetamines assays, where certain over-the-counter cold preparations may cross-react. Because of these possibilities, the impact that an inaccurate test result may have on the individual being tested, and the frequent need for a forensic rather than just a clinical test result, Varian, Inc. strongly recommends that confirmation testing be utilized when a preliminary positive result is obtained with an OnTrak or On-Site product and a confirmed result is necessary.
| 
