1 Specific urine toxicology techniques
2 Factors contributing to false-negative and false-positive test results
3 Approximate duration that drugs can be detected in urine
4 Alternate methods of screening for drug abuse
Urine toxicologies are recommended for pregnant women in order to provide optimal, comprehensive medical care and alcohol and other drug treatment.
They are, however, only an adjunct to good history-taking.
The use of urine toxicology can reduce morbidity that may result from misdiagnosis and the subsequent use of inappropriate medications, such as betamimetic tocolytics for premature labor.
The particular drugs for which a patient should be screened will depend on the specific geographic location and the substances most prevalent in that area.
Specific State laws may dictate approaches to the use of urine toxicologies.
Test results in some States and localities are used for other than medical purposes and may have legal implications (see Chapter 3 -- Legal and Ethical Guidelines for the Care of Pregnant, Substance-Using Women).
A toxicology test that is positive for drugs and/or alcohol -- whether it is a "true" positive or a "false" positive -- may have extremely negative effects on women, such as criminal detention or possible loss of child custody.
Because of this, the following guidelines recommend that urine drug testing be done only in cases where it is absolutely necessary.
Since current urine toxicology techniques vary in their specificity (the extent to which they produce false-positive results), the Consensus Panel recommends that the alcohol and other drug abuse field adopt the standards used for urine drug testing in the workplace.
These standards are contained in Mandatory Guidelines for Federal Workplace Drug Testing Programs, published in the Federal Register on April 11, 1988.
Training in these new tests and procedures should be conducted for all pertinent personnel.
Important issues related to urine toxicology include the need to uphold the civil rights of the patient and to ensure that there is informed consent for the procedure.
Testing a woman for illegal drugs in the absence of medical indications may be discriminatory, violate the woman's civil rights, and constitute an unlawful search and seizure.
The woman has the right, whenever possible, to be informed of the risks, potential ramifications, and benefits of urine toxicology testing.
There may be times when informed consent cannot be obtained because of medical considerations.
If urine is being tested for forensic rather than medical reasons, a separate consent should be obtained.
Before testing neonates, informed consent should be obtained from the mother.
Successful treatment for alcohol and other drug abuse depends on a positive therapeutic relationship between the patient and her caregivers.
Informed consent helps foster and is an integral part of a trusting and cooperative therapeutic relationship.
Urine testing is just one of a variety of ways of identifying a woman who is in need of treatment services.
Urine toxicology should never be the only reason for providing these services to a woman.
Caregivers should ask questions regarding the use of alcohol, other drugs, and medications as a routine part of any medical history.
Every effort should be made to identify which drugs are used; the frequency, pattern, and duration of use; last dosage; and the routes of administration.
It should be made clear to the patient that this information is necessary for proper medical management of the following:
Potential withdrawal, medical withdrawal, education, and alcohol and other drug treatment
Physical manifestations attributable to alcohol and other drug use
Potential interactions with other drugs or medications that may be given
Fetal and neonatal effects
A urine and/or blood toxicology screen is necessary only in those circumstances where a history of drug use cannot be reliably obtained, as when a patient is comatose or confused, or when a discrepancy exists between the clinical findings and the drug thought to have been ingested.
Caregivers should obtain informed consent and follow a closely monitored specimen collection procedure and chain of custody.
Reports indicate that a pregnant woman's race, ethnicity, and socioeconomic status have an overwhelming impact on whether or not she is screened.
The following are indications used by some programs to screen a pregnant woman for drug use:
History of alcohol and other drug use
Loss of custody of other children
No prenatal care
Altered mental state (e.g., incoherent, unconscious, lethargic, combative)
Preterm delivery; preterm labor; preterm, premature rupture of membranes
Third trimester vaginal bleeding (e.g., placental abruption)
Physical evidence of alcohol and other drug use (e.g., track marks)
Signs and symptoms of intoxication or withdrawal
A pregnant woman who is known to be using drugs, whether through self-report or positive toxicology, should be treated for the acute medical condition and referred for alcohol and other drug treatment.
In addition, a positive history of drug use or urine toxicology may suggest the need for a newborn toxicology screen, which may be ordered and obtained after delivery.
In a newborn, a positive toxicology for nonprescribed drugs suggests that a social work evaluation be done.
1 Specific urine toxicology techniques. Drug tests are most commonly performed on urine, since most drugs and their breakdown products are excreted in the urine in higher concentrations than in the blood.
While alcohol can be detected in the urine, testing of blood or breath is more widely used.
Screening tests: These are rapid, sensitive tests that may be lacking somewhat in specificity (i.e., there may be false-positive results) and may require confirmatory testing.
Thin Layer Chromatography (TLC).
TLC is a practical, economical, and sensitive method for detecting drugs in urine specimens.
Examples of drugs detectable with TLC and acid hydrolysis include heroin (detected as morphine), morphine, amphetamines, barbiturates, codeine, cocaine, glutethimide (Doriden), methadone, methaqualone (Quaalude), phenothiazine, and quinine.
Immunoassay techniques.
A variety of immunoassays and equipment are available to screen for drugs of abuse.
Laboratories may use enzyme immunoassays (e.g., Enzyme Multiplied Immunoassay Technique [EMIT]), radioimmunoassays, and fluorescence polarization immunoassays.
Examples of drugs detectable by immunoassays include opioids, amphetamines, cocaine metabolites, and phencyclidine (PCP).
Confirmatory tests: These are highly specific tests (i.e., false-positive results are rare when the tests are performed correctly).
Gas Chromatography/Mass Spectrometry: GC/MS is an example of a confirmatory test that allows for quantitative analysis.
Drugs detectable with GC/MS include opioids, amphetamines, cocaine metabolites, and phencyclidine, among others.
2 Factors contributing to false-positive and false-negative test results. How samples are collected and handled is critical for avoiding false-positive and false-negative test results.
Collecting samples: Improperly preparing the surfaces through which test materials are to be collected (e.g., using anesthetic lubricants for urinary catheters, cleansing skin with isopropyl alcohol) may cause false-positive results.
Handling samples: Mislabeling, switching, and dilution of samples may occur prior to testing.
Intermittent injections and diluted urine can result in false-negative results.
False-positive TLCs, although rare, may occur when spots of identical coloring and motility caused by different drugs are seen on the chromatograph.
Legally prescribed cough medications may yield a positive TLC for morphine, since a portion of the codeine is transformed into morphine in the body.
In addition, both false-negative and false-positive results can occur from certain foods a woman might ingest (e.g., poppy seeds).
If the patient has a bacterial urinary tract infection, a false-positive reaction with EMIT may occur with each test, indicating polydrug use.
When there is an actual or potential urinary tract infection, the presence of lysoenzyme should be determined to rule out the possibility of a false-positive reaction.
Finally, the expertise of the testing laboratory may determine the reliability of the results.
Even the best laboratories have a relatively high incidence of nonreproducible results.
3 Approximate duration that drugs can be detected in urine. The following table shows the approximate duration for detecting a number of drugs in the urine of non-pregnant adults.28
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