When it comes to drug testing, both urine and hair tests are widely used in workplace drug screening, rehabilitation centers, and legal contexts. These tests rely on specific cut-off levels to determine whether a drug test result is positive or negative. Understanding these cut-off levels is crucial to ensure fair and accurate testing practices.
What Are Cut-Off Levels?
Cut-off levels refer to the minimum concentration of a drug or its metabolite that must be present in a sample (urine or hair) for the test result to be considered positive. If the detected substance is below this threshold, the test result is reported as negative. Cut-off levels help to avoid false positives from passive exposure or trace amounts.
Urine Drug Testing: Australian vs. US SAMHSA Guidelines
Urine drug tests are commonly used because of their non-invasive nature and the wide range of substances they can detect. Both Australian Standards (AS/NZS 4308) and SAMHSA outline cut-off levels for various drug classes, but there are slight differences between the two.
The Australian Standard for urine drug testing provides cut-off levels for workplace drug screening across Australia and New Zealand. Below are the cut-off levels for common drugs:
| Screening | |
| Amphetamines | 300 ng/mL |
| Cocaine and its metabolites | 300 ng/mL |
| Cannabis (THC) |
50 ng/mL |
| Opiates (morphine, codeine) | 300 ng/mL |
| Methamphetamine | 300 ng/mL |
| Benzodiazepines | 200 ng/mL |
These thresholds ensure the accuracy of test results while reducing the risk of false positives from passive exposure or minimal drug use.
The SAMHSA guidelines are the foundation of workplace drug testing in the United States. The following are the cut-off levels for urine tests based on the latest SAMHSA regulations:
| Screening | |
| Amphetamines | 500 ng/mL |
| Cocaine and its metabolites | 150 ng/mL |
| Cannabis (THC) |
50 ng/mL |
| Opiates (morphine, codeine) | 2,000 ng/mL |
| Methamphetamine | 500 ng/mL |
| Benzodiazepines | Not included in SAMHSA panel |
One notable difference is in the detection threshold for opiates, where SAMHSA has a higher cut-off of 2,000 ng/mL to reduce false positives from substances like poppy seeds.
Hair Drug Testing: A Longer Detection Window
Hair drug testing offers a much longer detection window than urine testing, often going back up to 90 days. The cut-off levels for hair testing are typically lower than urine tests due to the long detection window. Both Australian standards and SAMHSA guidelines provide detailed thresholds for hair testing.
Australian hair testing cut-off levels (typically based on AS/NZS 4760) include the following:
| Screening | Confirmatory | ||
| Amphetamines | 0.2 ng/mg | Amphetamines Methamphetamine MDA MDMA |
0.2 ng/mg |
| Cannabinoids | 0.1 ng/mg | THC THC-COOH |
0.05ng/mg 0.0002 ng/mg |
| Cocaine | 0.5 ng/mg | Cocaine BZE, EME, CE, NC |
0.5 ng/mg 0.05 ng/mg |
| Opiates | 0.2 ng/mg | Morphine Codeine 6-acetylmorphine |
0.2 ng/mg |
| Methadone | 0.2 ng/mg | Methadone EDDP |
0.2 ng/mg 0.05 ng/mg |
| Buprenorphine | 0.01 ng/mg | Buprenorphine Norbuprenorphine |
0.01 ng/mg |
US Quest Lab Hair Testing cut-off levels include the following:
| Screening | Confirmatory | |
| Methamphetamine | 0.5ng/mg | 0.5ng/mg |
| MDMA | 0.5ng/mg | 0.5ng/mg |
| Amphetamine | 0.5ng/mg | 0.5ng/mg |
| MDA | 0.5ng/mg | 0.5ng/mg |
| Cocaine / Metabolites | 0.5ng/mg | 0.5ng/mg |
| Benzoylecgonine | 0.5ng/mg | 0.5ng/mg |
| Opiates | 0.2ng/mg | 0.2ng/mg |
| 6-Acetymorphine (6-AM) | 0.2ng/mg | 0.2ng/mg |
| Oxycodone | 0.2ng/mg | 0.2ng/mg |
| Phencyclidine (PCP) | 0.3ng/mg | 0.3ng/mg |
| Marijuana Metabolite | 0.001 ng/mg | 0.0001 ng/mg |
Hair testing is preferred in cases where long-term drug use needs to be evaluated, such as during rehabilitation or in legal cases. It also minimizes the chance of cheating or tampering with the test sample.
Cut-off levels are essential in drug testing as they help laboratories and employers determine whether a test result is positive or negative. Understanding the differences in cut-off levels between Australian standards and US SAMHSA guidelines ensures that you choose the most appropriate and accurate testing protocol for your specific needs.