Despite the existence of sophisticated drug-testing methods, it is still possible to obtaining incorrect test results and to detect adulterated urine samples.
Typically, GC/MS is preceded by a rapid immunoassay method to eliminate the majority of the "negative" samples.
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 confiramto0ry testing.
Selection of the drug top be tested should depend on the local availability of the drug, its abuse potential and clinical effects, as well as on the availability of analytical technology and expertise in testing and in interpreting laboratory results.
Moreover, it is difficult to determine the route of drug administration, quantity or frequency, as well as when the drug was taken, on the basis of the laboratory results.