Drugs and alcohol test

Although urine tests are far from infallible, it is difficult to challenge positive test results. "False positives," in which workers are wrongfully accused of marijuana use, are highly unlikely so long as labs exercise proper care. The standard procedure is to first screen the samples with an immunoassay test, then confirm positive results with the more accurate gas chromatograph mass spectrometer. This virtually eliminates the chance of false positives in exchange for a relatively high rate of "false negatives," where drug use is not detected. The sensitivity of the test is determined by the concentration of metabolites it is set to detect: for the Dept. of Transportation, the standard cutoff is 50 nanograms/milliliter (ng/ml).

No substance is known to produce a false positive for marijuana. It used to be that ibuprofen (Advil, Motrin, Nuprin) interfered with the marijuana test, but this problem has been fixed. A variety of over-the-counter medicines can cause false positives for amphetamine and other illicit drugs on the EMIT test, but not on the GCMS.

"Passive smoking" of marijuana is not an acceptable excuse at the 50 ng/ml level, since only in extreme circumstances can a non-smoker absorb enough pot to test urine positive (e.g., being stuck in a closet full of heavy smokers for hours). However, passive exposure may result in positive tests at 25 ng/ml or lower.

The detection windows depend upon multiple factors drug class, amount and frequency of use, metabolic rate, body mass, age, overall health, and urine pH. For ease of use, the detection times of metabolites have been incorporated into each parent drug. For example, heroin and cocaine can only be detected for a few hours after use, but their metabolites can be detected for several days in urine. In this type of situation, we will report the (longer) detection times of the metabolites.

Oral fluid or saliva testing of drug use results for the most part mimic that of blood. The only exceptions are THC and benzodiazepines. Oral fluid will likely detect THC from ingestion up to a maximum period of 18–24 hours. Low saliva:plasma ratio continues to cause difficulty in oral fluid detection of benzodiazepines.

Urine cannot detect current drug use. It takes approximately 6–8 hours or more post-consumption for drug to be metabolized and excreted in urine. Similarly, hair requires two weeks, and sweat, seven days.

If you're in doubt please few simple questions: Am I drug addict? or Do I have drinking problem?"