Drug tests are conducted mainly to test people systematically or falling relative to possible abuse. The tests are performed in the following: certain groups of people, mostly students, athletes and prisoners people who apply for certain jobs (. Eg pilots, commercial truck drivers) people in in vehicle or boat accidents or in accidents involved working people who have made a suicide attempt with unknown substances were people in a court-mandated treatment program or in connection with a suspended (to ensure compliance with abstinence monitor) people (in a drug rehabilitation program as a standard measure to objective knowledge about substance abuse receive and to optimize treatment) people, including minors, who must participate in a court order in a drug screening. The members of the military notification or consent can be a prerequisite before the test begins, depending on the jurisdiction and the circumstances. Pure documentation purposes may be sufficient legal, but the tests can not give information about the frequency or intensity of the substance means consumption. So you can not determine the severity of abuse. In addition, drug tests involve only a limited number of substances and can not detect some other substances. The physician must therefore use other measures (eg. As a thorough medical history, questionnaires) to determine the extent to which the drug affects the life of the patient. The substances for most commonly tested include alcohol, amphetamines cocaine Marijuana Phencyclidine Natural and semi-synthetic opioids tests for benzodiazepines and barbiturates also be carried out. Urine, blood, breath, saliva, sweat or hair samples can be used. Urine tests are most often used because they are not invasive, about to capture high quickly and in a position a wide range of substances. The detection window depends on the frequency and amount of income, but normally for most drugs for 1 to 4 days. Because cannabinoid metabolites are detectable for a long time, urine tests for marijuana may be far from positive after use. Blood tests can be used to quantify levels of certain drugs. However, they are less frequently performed because this investigation is invasive and, the time window for the detection of many drugs is often much shorter only a few hours. The hair analysis is not as widespread, but represents the longest time window of detection, ? 100 days for some substances. The validity of the test depends on the type of examination. Screening tests are usually of rapid qualitative urine immunoassays. Such screening tests are associated with a number of false-positive and false-negative results, and they do not recognize the opioid meperidine and fentanyl. Also, lysergic acid diethylamide (LSD), gamma hydroxybutyrate (GHB), mescaline and inhalation hydrocarbons in rapid tests are not detected. Confirmation tests requiring several hours, typically use gas chromatography or mass spectrometry. Incorrect results Various factors can lead to false-negative results, particularly in urine tests. Patients can provide samples of other (presumably drug-free) humans. This possibility can be addressed by the directly observed sampling with an immediate sealing of the samples with tamper-proof seals. Some people try to falsify urine drug tests by drinking large amounts of fluids or diuretics before the test. However, samples that appear to be clear, can also be rejected by the lab. False-positive results can be caused by taking prescription and non-prescription drugs and the ingestion of certain foods. Poppy seeds can cause false-positive results for opioids. Pseudoephedrine, tricyclic antidepressants and quetiapine can cause false positive results for amphetamines, and ibuprofen can cause false-positive results for marijuana. With a cocaine test benzoylecgonine, the primary metabolite, recognizes cause other substances no false-positive results.