Specimen integrity is a key component of a reliable and accurate drug screen. The test is only as good as the specimen. Urine is a reliable specimen for drug screens, mainly because the drugs can be detected for a longer period of time (several days). Blood and saliva specimens are more reflective of impairment, but detection time is usually only a few hours after ingestion. Anyone conducting urine drug screening needs to be aware of the possibility of intentional adulteration by the donor. Adulterants may affect the drug screen test results, most often causing false negatives. Confirmations by mass spec can overcome many methods of adulterations. Dilution of the urine specimen is done to try to get drug level below the cutoff of screening assays. Dilution can be accomplished by adding water to the specimen after collection or by drinking lots of water prior to collection. Determination of creatinine in the urine specimen is used to detect dilution. Even if diluted, the mass spec can measure drug levels far below screening cutoff concentrations. Testing for the most common adulterations is reliable and commonly offered by most laboratories. Substitution by the donor with someone else's urine is another tactic to avoid detection of unauthorized drug use. DNA testing is the only way to positively identify the donor. Cheating on a drug screen may be unlikely in patients seeking treatment for pain management. One reason to follow precautions is that these procedures give credibility to the testing that regulatory agencies expect to see. Proper collection can prevent the opportunity for adulteration. Chain of custody procedures are only needed for drugs screens that may be used in court. The clinical specimen is usually admissible in court.