How accurate is a GC MS drug test?

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.

Can a GC-MS test be wrong?

GC-MS is a very specific test to identify separate compounds within a sample. However, GS-MS can also lead to a false negative if the GC-MS column is not designed to identify all potential compounds.

Does GC-MS test for everything?

GC/MS can measure the amount of every chemical present in a given sample simply by comparing the particular chemical to pre-measured standard. GC/MS identifies any unknown chemical in the sample.

How is GC-MS used in drug testing?

The GC/MS process produces a detailed report of the chemicals found in the urine sample, even listing the number of nanograms of each compound present in the sample. All negative tests showing no drugs present are entered into the Automated Results Program.

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When is GC-MS used in drug testing?

The most sophisticated drug-testing approach is gas chromatography coupled with mass spectrometry (GC/MS), which is regarded as a “gold standard”; it is used in confirmatory testing. Typically, GC/MS is preceded by a rapid immunoassay method to eliminate the majority of the “negative” samples.

Can you fight a false positive drug test?

The best way to contest false-positive results is to reach out to your pharmacist and ask if prescription drugs and OTC medications you take on a regular basis can cause a positive drug test result. Ask if the pharmacist can provide written documentation to this effect and bring a copy to the test site.

What does GC MS confirm test level mean?

A GC/MS or LC/MS confirmation test is legally defensible evidence of drug use. The confirmation testing rules out false positive claims like poppy seeds, hemp products and over the counter medications. The MRO Process. At this point, the positive drug test result is sent from the lab to the Medical Review Officer (MRO) …

How long does GC MS take?

» How long does it take for results? Results are typically reported in 24 hours1 for negatives, 24-72 hours for positives6. All presumptive positive results go through a confirmation process to ensure accurate results.

What is an advantage of GC MS?

Analyzing small and volatile molecules

When combined with the detection power of mass spectrometry (MS), GC-MS can be used to separate complex mixtures, quantify analytes, identify unknown peaks and determine trace levels of contamination.

What is the principle of GC MS?

The GC works on the principle that a mixture will separate into individual substances when heated. The heated gases are carried through a column with an inert gas (such as helium). As the separated substances emerge from the column opening, they flow into the MS.

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How do you read GC MS results?

How to Read GC/MS Chromatograms

  1. The X-Axis: Retention Time. Usually, the x-axis of the gas chromatogram shows the amount of time taken for the analytes to pass through the column and reach the mass spectrometer detector. …
  2. The Y-Axis: Concentration or Intensity Counts. …
  3. Differences in Gas Chromatogram Models.


How much does a GC MS test cost?

As a rough approximation metals analyses usually run between $25 and $75 per sample, and LC/MS/MS and GC/MS/MS analyses are typically between $100 and $200 per sample. For lipidomics, the cost for running a quantitative analysis (targeted analysis of known lipids) is $120 per sample.

What’s the cutoff levels for drug testing?

In the case of urine analysis, drug testing cutoff levels are measured in nanograms per milliliter (ng/ml). For example, an initial screening for marijuana must show at least 50 ng/ml, and then confirmatory tests must prove at least 15 ng/ml.

What drugs are detected in a drug screen?

The drugs most often tested for include:

  • Marijuana.
  • Opioids, such as heroin, codeine, oxycodone, morphine, hydrocodone, and fentanyl.
  • Amphetamines, including methamphetamine.
  • Cocaine.
  • Steroids.
  • Barbiturates, such as phenobarbital and secobarbital.
  • Phencyclidine (PCP)


What is the minimum amount of urine needed for a drug test?

Urine drug test collections

Urine testing requires a minimum of 30 mL of urine (45 mL for a US Department of Transportation or DOT collection) collected in the privacy of a restroom. The collector pours the specimen into a bottle that is sealed with tamper-evident tape.

How long does it take for urine drug screen results?

Negative screening results are often released within 24 hours and non-negative screens are typically released within an additional 24 to 72 hours. Q: Can a urine drug test be beaten or adulterated? A: While it is the most common drug testing method, urine testing is not foolproof.

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