Drug testing is used by courts, concerned parents, and places of employment to determine if an individual has been using drugs.  The two Drug testing methods most widely used are Hair Analysis and Urine Analysis.  Each test, although taken by different methods, determine if there are certain substances or metabolites in a person’s system as a result of using certain drugs.
In testing for hair, a sample of hair as close to the scalp as possible is gathered.  It should be around two inches long, with approximately 120 strands of hair needed for an accurate analysis.  The sample of hair would be rejected if not long enough or if it is contaminated with lice. Hair collected from a hair brush cannot be used. The hair collected from body parts other than the hair has not been determined to be reliable because the growth rate and rates of incorporation of drugs into the hair from other locations has not been studied as extensively as that of head hair.
This first method of testing is called Enzyme- Linked Immunosorbent Assay or ELISA.  Samples that test positive in the initial screening process are retested using a more intensive testing method.  This method is called gas chromatography/mass spectrometry/mass spectrometry or GC/MS/MS.  It is a more intensive testing method is used to ensure reliability of the test results.  It is more expensive method of testing and therefore is only used as means to confirm initial positive results.
The turnaround time (time results are known) is consistent with urinalysis.  Negative results should be known within twenty four hours of receipt and positive results are confirmed within forty eight-seventy two hours of receipt.  The drugs that are tested for include: Amphetamines (Amphetamine, Methamphetamine, Ecstasy, MDMA and MDA), Opiates (Codeine and Morphine), Cocaine (and Cocaine metabolites), Marijuana metabolite (THC), and PCP.
Hair tests are able to detect drug use from four days to ninety days.  When you compare it to urinalysis, hair tests are limited in being able to detect more recent use.  Urinalysis is able to determine substances as soon as twenty four hours (depending on the substance), while hair analysis is unable to detect for up to four days back (depending on hair growth).  If someone tests positive for substances, urinalysis would be better suited to monitor future substance usage as opposed to hair analysis.