Drug testing may be used to detect past drug use or current dysfunction. Pre-employment mass screenings, for example, are oriented toward detecting a pattern of drug use in the past rather than current impairment. Post-accident testing is intended to detect current impairment. Drug testing in a criminal context emphasizes accuracy, and forensic or legal standards are required.

Terminology
Drug testing is a highly technical field, involving complex issues in both law and chemistry. Hence it is important to understand precisely how some of the common phrases are used. For example, Òpre-employment screeningÓ is used to refer to a testing program while Òscreening testÓ is used to refer to a preliminary and usually less expensive method which is confirmed by a subsequent and usually more expensive method.

Observation
Observation of the urine as it is being collected is required to meet chain of custody requirements, . Without observation one cannot be sure the urine has not been tampered with to create a false negative, or that it is really the urine of the person in question. Until recently, observed collection was rare except in criminal justice situations. Whenever direct observation has been used in the workplace, there has been a loud outcry. People feel humiliated and degraded by the process. Indirect observation procedures can be used, together with other precautions, such as searching clothing, washing hands of the subject, and measuring temperature of the sample.

Drug Urinalysis
Urine drug screening is an analytical tool for detecting the presence of drugs and their metabolites in urine. The technology for performing urinalysis varies, and can be designed to meet the specific needs of individual clients. A major limitation of urinary drug tests is their lack of specificity, unless a GC/MS is used. Urine tests are less able to detect when the drug was taken than blood tests. There is considerable individual variability in detection times. Diet, urine flow, and dose dependency can alter the test results. Some people test positive at lower doses than others, for example.

Direct Observed
Collection The Mandatory Federal Guidelines allow an immediate second collection under direct observation when the temperature of the specimen is outside the acceptable temperature range and the donor either refuses to allow the collector to measure his or her body temperature or the donor's body temperature does not explain the specimen temperature. The collector can also demand a second sample under direct observation when the collector believes that the donor adulterated or substituted the specimen provided. This can occur when there is bluing color in the specimen, when the collector hears or smells something unusual while the donor is providing the specimen or when the collector sees an adulterating substance on the floor. Direct observation with prior notice is also allowed when the specimen provided by the donor on a previous drug test was reported by the lab to have been diluted, adulterated, or the test was not performed because the specimen was unsuitable for testing and the Medical Review Officer (MRO) determined that no medical explanation exists for the specimen's unsuitability.

Dedicated Bathroom
A dedicated bathroom is one solution to the observation problem. This is a bathroom with all water supply cut off, so that urine cannot be diluted. Before entering, the person giving the sample leaves behind coats, purses, and any other obvious hiding places for ÒcleanÓ samples or diluting agents. Such precautions increase the probability that the sample cannot be altered. However, the person can still wear a colostomy bag containing drug-free urine or hide contaminating substances under the fingernails. A substituted sample may be detected by measuring the temperature, unless it is given at body temperature. Most contaminants can be detected if they are suspected. But carefully planned attempts to foil the dedicated bathroom may succeed.

Shy Bladder
Occasionally, a donor is unable to provide a specimen because he or she either urinated recently or has a "shy "bladder. Generally, the term refers to an individual who is unable to provide a sufficient specimen either upon demand or when someone is nearby during the attempted urination. The collector is required to keep records of each attempted urination. The donor is given large quantities of fluids, such as 8 ounces every 30 minutes up to 24 ounces and 2 hours. Donors who cannot provide a sample can be reported as refusing to provide a sample.

Chain Of Custody
Chain of custody is a monitoring process to prevent tampering with the sample or the results. Chain of custody begins with collection of the urine, and continues through the final reporting of test results to clients. Sealing of sample containers, transport and control of samples, receipt of samples by the laboratory, and supervision of lab tests remain under strict discipline throughout the chain of custody. Authorized signatures are required at each step. Laboratory results can be effectively challenged in court if there are weak links in the chain. Standards regulate the handling, analysis, and collection of samples if they are intended to be admissible in a court of law. Transfer of urine, blood, or saliva from the subject to the container must be witnessed. For example, if a person is taken to a physician for a blood sample, the physician becomes the first link in the chain of custody. Few physicians understand the legal chain of custody procedures. Unless otherwise instructed, they will usually follow clinical laboratory standards, which will not stand up to challenge by a knowledgeable attorney. The person collecting the blood sample must be able to testify regarding the collection procedure. Likewise, the person collecting the sample must be able to testify to the accuracy of the container label, including the subjectÕs name and other identifying information, such as date, time of the collection, and type of collection receptacle. The chain of custody must be maintained until the specimen reaches the laboratoryÑand through the confirmation of initial results.

Custody and Control Form
Over time chain of custody forms became a nightmare because employers used different forms. This problem was corrected with rules which mandate the use of an approved Custody and Control Form (CCF) to be used to document the collection of a specimen at the collection site. The OMB-approved (Office of Management and Budget) CCF is usually supplied by the testing lab. The OMB-approved CCF may not be modified. The Urine Specimen Collection Handbook for Federal Workplace Drug Testing Programs can be ordered from the National Clearinghouse for Alcohol and Drug Information (NCADI) and is available at the NCADI web site <www.health.org/workpl.htm>.

Detection Period
The length of time a drug or metabolite can be found in bodily fluids is known as the detection period. Detection periods vary widely according to the inherent physical and chemical properties of the drug itself, the personÕs history of use, and characteristics such as age, sex, body weight, and health. For example, the cocaine detection period is very short (12 to 48 hours) whereas marijuana has a longer detection period, depending on drug-use history. Casual marijuana use can be detected from 2 to 7 days later with chronic use, detection may be possible up to two months after the last use. However, a single puff of low potency marijuana may be undetectable after 12 hours. Detection times is of intense concern to employers because it indicates how long after illicit drug use that use can be detected and therefore how confident the employer can be that employees tested negative are actually drug free at the time of testing. For employees who have used illicit drugs, knowledge of detection times can mean the difference between being detected and slipping by. Drug using employees usually consult detections times tables to determine how long they must abstain from use when facing a drug test with the hopes of testing negatives. This cat-and-mouse game is found most often in pre-employment testing where an applicant will clean-up for a few weeks before applying for employment. Metabolite And Metabolism After a drug is swallowed, smoked, injected, or snorted, it is distributed throughout the bloodstream. As the blood repeatedly passes through the liver and other parts of the body, the drug encounters numerous enzyme systems, which convert most of the drug into one or more end products called metabolites. Metabolites travel into various parts of the body, including urine, blood, and hair. How long it takes for this to occur depends on metabolism, and the length of time the metabolites stay detectable in the system is called detection time.

Sensitivity And Specificity
Test sensitivity is a measure of the smallest amount of the drug that can be detected in the urine sample. Specificity of a test is its ability to distinguish one drug from another. Sensitivity of the screening test should be set appropriately for the goals of the test.

Cut-Off Level And Detection Limit
Cut-off level and detection limit are two factors influencing a testÕs sensitivity. Cut-off level refers to the concentration of a drug necessary to indicate a positive reading on the test. Detection limit of the test is the concentration below which a particular drug is undetectable by the method. Typically the first test given is for broad screening and is inexpensive. These include the EMIT¨, TLC, or RIA which are relatively sensitive, and can detect most drugs or metabolites in the system. They give an on-off, positive or negative result. If there is a positive, it should be confirmed by a different test. The most credible confirmation is GC/MS, which is considerably more expensive. The confirmation test used should be more specific in its results. There are volume discounts available on large numbers of similar tests from the same accounts. On the other hand, specially designed tests which have to conform to rigorous standards is very much more expensive.

False Positives And False Negatives
Clerical and laboratory errors can be made anywhere in the process from collection, identification of the sample, to reporting of the results. "False positiveÓ means that a drug-free sample was reported positive for drugs. ÒFalse negativeÓ means that a sample containing drugs was reported as drug-free. ÒFalse positivesÓ should not be used loosely to mean an inaccurate or misleading result. For example, a positive screening result for amphetamines or opiates due to over the counter or prescription drugs is not a false positive if these over-the-counter medications were in fact consumed.

Confirmation Of Positive
Results All urine samples reported positive should be analyzed a second time by a different testing method. Both tests must give a positive result before a positive report is made. This process is called confirmation.

The Collector
The Mandatory Guidelines define a collection site person as a person who instructs and assists individuals at a collection site and who receives and makes an initial examination of the urine specimen provided by those individuals. The collector, who does not have to be a medical professional, must receive specialized training in collecting urine specimens. When a collection is required to be performed under direct observation, the collector must be of the same gender as the donor.

Collection Site
The term collection site refers to the entire facility used to collect the urine specimen, which includes the rest room or toilet stall and the work area used by the collector. The site must restrict access to only authorized personnel and collection materials and supplies. The collector must ensure that the donor does not have access to items, such as soap, disinfectants, personal hygiene products and water, that could be used to adulterate or dilute the specimen. Unobserved entrance and exit from the site must be prohibited. The site must allow for secure handling and storage of specimens from collection until shipment to the testing lab. In preparation of the site, any water supply available must be controlled to prevent the donor from diluting the specimen. Whenever possible bluing or other color agents must be added to any water supply available to the donor.

Donor Identification
The donor must be positively identified as the individual selected for testing. Acceptable methods of identification are photo identification including driver's license, and employee badge, positive identification by employer representative, or other identification allowed under the employer's workplace testing program. Identification by a co-worker or another donor is not acceptable. Non-photo identification cards such as social security card, credit card, pay vouchers, or voter registration cards are not acceptable.

Fatal Flaws
The following errors or omissions in the documentation for a sample are considered fatal flaws that result in a specimen being rejected for testing by the lab.

Other errors or omissions may be fatal flaws unless the information can be recovered and/or provided by the collector to the lab in writing.

Medical Review Officer
An essential part of the drug testing program is the final review of results. A positive laboratory test result does not automatically identify an employee of job applicant as an illegal drug user. An individual with a detailed knowledge of possible alternative medical explanations is essential to the review of results. The Medical Review Officer (MRO) fulfills this function by reviewing the results with the donor and protecting the confidential nature of the donor's medical information. The MRO is considered a critical safeguard in the Federal Drug Testing Program. The function of the MRO is described in the Medical Review Officer Manual for Federal Workplace Drug Testing Program prepared by the Substance Abuse and Mental Health Service Administration (SAMHSA).