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Drug Screening in the USA - 1994

Drug screening in the USA began in the 1970s as an attempt to curb the spread of drug abuse in the US military forces in Vietnam. The Navy started screening after an accident on the carrier Nimitz revealed that a number of sailors and airmen were taking mind-altering drugs. In 1986 all Federal government employees were included in mandated drug screening programs. By 1994 drug screening had been extended to all workers in industries regulated by the Federal government (nuclear energy, petroleum, aviation, railroad, maritime and road transportation etc.). It is estimated that 50-75% of medium to large US companies have employee drug testing programs.

Urine as the specimen of choice

The best specimen for therapeutic drug monitoring or for forensic toxicology is blood. It was evident that it would be impractical to take blood from millions of workers to be covered by the drug screening program. Taking urine samples is less invasive.

The goal of the program was to determine a history of drug use rather than to confirm drug intoxication. The presence of low levels of urine metabolites of drugs of abuse can indicate exposure which occurred days or weeks before, even when there is no question of present drug intoxication or fitness for duty.

The designation of urine as the only acceptable specimen for drug screening was made law in 1988 [1]. In addition to strict rules for collection and preservation of unadulterated urine specimens, testing protocols were mandated. Urine may be used for cannabinoids, opiates, cocaine, amphetamines and PCP only. The initial test must be an immunoassay followed by confirmation of positive specimens by GC/MS.

Using urine specimens focussed everyone on urinary metabolites and set drug cut-off concentrations appropriate for urine only. They forgot about active drug and active metabolites found in blood, sweat, saliva or hair. Methods now available tend to conform to the characteristics of enzyme immunoassay tests used by the US military in the 1970s; many other exciting developments have been slowed because of the US concentration on urine.

Laboratory accreditation for drug screening

The HHS Mandated Guidelines [1] dictate specimen choice, collection, testing procedures and interpretation of results. All laboratories which test employees covered by the Federal drug screening program must be accredited as following these guidelines. Most private industrial drug screening programs have adopted these same requirements. Accreditation is achieved by on-site inspection every six months and a proficiency testing program consisting of ten urine specimens sent three times a year. A laboratory which gets a false positive result loses its accreditation.

Over 90 laboratories across the USA currently maintain accreditation in this program. Review and grading of both inspections and proficiency tests by a central group ensures that any urine drug screening test performed anywhere in the USA will follow the same procedures and produce the same results. This is perceived by the public as ensuring fairness in the drug screening program.

Cost effectiveness depends on prevalence

Drug screening has invaded the privacy of workers not charged with any crime. Drug screening costs millions in laboratory test fees and has narrowed the availability and acceptability of drug tests used in the USA. Is it worth the cost?

The effect of a pre-employment urine drug screening program for the US Postal Service was published in JAMA [2,3]. It involved 2537 workers employed in Boston whose employment history was followed for about 400 days. The results of drug screening were blind to the management. Specific end points were time to termination (dismissal or resignation), absence rate, time to first work-related accident and injury and time to first reported disciplinary action.

Analysed separately for marijuana, cocaine and other drug use compared with employees who had negative drug tests on the pre employment screen, there were significant differences. Drug users overall had an absenteeism rate twice as high as non drug users. Marijuana users left employment earlier, had more accidents and injuries, had a poorer disciplinary record and more absences (all statistically significant; see above). Cocaine users had significantly more injuries and greater absence, while other drug users had a significantly worse disciplinary record.

The cost benefit analysis showed that a positive effectiveness ratio depends upon the prevalence of drug use in the subject population. For the US Postal Service this occurs for a population which has a prevalence of drug abuse of 5% or higher. Cost saving was $162 per applicant hired over one year but industries with high accident costs could benefit more.

Before the start of drug screening in the US military, surveys showed a prevalence of drug use of 47% [4]. When random testing was begun, the positive rate was 22%, a figure which steadily declined every year to 2.5% after six years of testing [4] and to less than 1% today.

Some of the apparent decline has been offset by the use of drugs which are not detected in the screening tests. For example, the young recruits substituted MDMA (Ecstasy) for cannabis, LSD for PCP and pethidine or fentanyl for heroin.

The program has been able to follow drug abuse patterns by adding tests, changing the frequency of screening tests and the cut-offs used. For instance, screening for LSD was instituted in 1990 in the Navy when it was found that LSD was being smuggled aboard ships at sea. The US Navy has largely achieved its goal for drug abuse, "Not on my watch, not on my ship, not in my Navy!"

The Federally mandated employee testing has not shown similar flexibility since its technical requirements are mandated by law rather than by executive command. While drug screening positive rates in the military are constant at about 1-2% positive results (probably lower than prevalence in the population in general), pre-employment testing has shown a lowering of positive rates from 17% to about 10%. This may, however, be a simple reflection of greater unemployment among older workers in recent years rather than deterrent effects of drug testing; most drug use is in the population of 18-30 year old, non-Caucasian males.

Private sector employee drug testing programs have been shown to improve workplace safety and employee productivity, as well as to decrease health benefits costs, absenteeism and employee turnover [5].


In selected populations prone to drug use (prevalence greater than 5%) random urine drug screening can identify incorrigible drug users and deter others from the abuse of drugs. This results in greater public safety and reduced health care costs.

Vina Spiehler PhD Newport Beach, California


  1. Mandatory Guidelines for Federal Workplace Testing, Department of Health and Human Services. Federal Register 1988 53: 11970.
  2. Zwerling C, Ryan J, Orav EJ. The efficacy of preemployment drug screening for marijuana and cocaine in predicting employment outcome. Journal of the American Medical Association 1990 264:2639-43.
  3. Zwerling C, Ryan J, Orav EJ. Costs and benefits of pre-employment drug screening. Journal of the American Medical Association 1992 267: 91-3.
  4. Irving J. Drug screening experience in the military. Clinical Chemistry 1988 34: 637-40.
  5. Sunshine I. Mandatory drug testing in the United States. Forensic Science International 1993 63: 1-7.

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