Urine toxicology, legal issues, and professional practice

Urine toxicology

Toxicology is the study of poisonous substances and drugs and their effects on the body. The clinical laboratory performs tests on body fluids and tissues to monitor the use of therapeutic drugs, such as antibiotics, anticonvulsants, antidepressants, and barbiturates. They may also test for poisoning by herbicides, metals, animal toxins, and poisonous gases (e.g., carbon monoxide).

Laboratory testing for illegal drugs or alcohol is also done, most commonly due to employment, insurance, or legal requirements. A urine specimen is the most reliable choice for most routine screening procedures. Urine drug tests detect drug metabolites and not the drugs themselves. A metabolite is a by-product of drug metabolism. Urine samples will remain positive even after the effects of the drugs are gone. For routine screening, a random specimen is usually collected.

Often, the following safeguards are used to ensure that a specimen is fresh and is truly from the patient:

• Bluing agents may be added to the toilets.
• A sealed container with a temperature-sensitive strip may be provided for collection.
• Someone of the same gender may accompany the patient into the restroom during the collection.

Additional measures that limit access to water in the restroom are covered under the chain-of-custody rules later in this chapter.

Legal specimens require a chain of custody protocol, detailed later in this chapter. Drugs and their metabolites often remain in urine much longer than the physical impairment lasts, which is one reason urine screening is favored over blood screening.

As a medical assistant, you may be responsible for collecting specimens for toxicology tests and for performing certain laboratory tests, though which tasks you may perform is delegated by the supervising provider within the limits of state law and the test’s CLIA complexity rating. Rapid drug screening devices are about the size and shape of a credit card and are CLIA-waived, which is why running one is within an MA’s scope of practice; confirmatory testing on a positive result uses more specific methods and is sent to a higher-complexity reference laboratory. The device is dipped into a urine sample, or urine is directly applied to the device, and results are read according to the manufacturer’s instructions in just minutes.

Each device has a control © band and a test (T) band. The C band must show a line for the result to be valid - if it doesn’t, the test failed and must be repeated. A negative result shows a line in both the C and T bands: none of the targeted drugs were found in the urine sample at a detectable level. Inconclusive results indicate that the device reacted with something in the urine, and confirmatory testing is needed.

Urine multidrug screening tests are a type of lateral flow immunoassay that tests for urine metabolites of a variety of drugs. Common drugs tested include amphetamines, barbiturates, benzodiazepines, cocaine, morphine, methadone, phencyclidine (PCP), tricyclic antidepressants, marijuana, Ecstasy, methamphetamines, oxycodone, and opiates. This type of testing is also an immunoassay in which antibodies and antigens react to form a readable test result. By using antibodies specific to different drug classes, some test cartridges can simultaneously detect up to 10 different drugs from a single sample in 5 minutes.

Example: Reading a rapid drug screen

A urine multidrug screening cartridge shows a line in the C band and a line in the T band.

Answer: This is a negative result. The C-band line confirms the test ran correctly, and the T-band line means no targeted drug was detected above the cutoff level. If the T band showed no line instead, that would be a presumptive positive requiring confirmatory testing.

Adulteration testing and chain of custody

Drug testing has legal consequences; therefore additional testing may be necessary to ensure that samples have not been adulterated. Adulteration is the intentional manipulation of a urine sample that allows someone to falsely pass a drug screening test. It may involve using urine from another person or an animal, diluting the sample with water, or adding other substances that would compromise the test procedure.

Sensitivity limits for drug screening are set by the US Substance Abuse and Mental Health Services Administration (SAMHSA), the National Institute on Drug Abuse (NIDA), and the US Department of Health and Human Services (DHHS). Positive results on urine drug samples should be confirmed with more specific confirmatory testing methods.

Chain of custody rules

1. The individual being tested must provide photo identification.

2. Indirect observation of specimen collection is important to make sure the patient being tested has provided the sample. Indirect methods of observation include the following:

   1. Measuring the specimen’s temperature

   2. Securing water faucets in the restroom so that urine cannot be diluted

   3. Having the patient remove outer clothing and leave personal belongings in the examination room

   4. Not allowing water to be run or the toilet to be flushed in the restroom during the collection

      Note: If you suspect the sample has been adulterated, the patient may be asked to provide another specimen.

3. Within 4 minutes of receiving the specimen, check its temperature (the range should be 32° to 38°C [90° to 100°F]). The sample volume should be a minimum of 30 to 45 mL. Inspect the sample for any indications of adulteration (e.g., an unusual color, the presence of foreign materials).

4. Pour the specimen into a specimen bottle and seal the lid with the tamper-evident label/seal provided at the bottom of the chain of custody form. The donor should be present when this is done and should see you write the date and your initials on the label.

5. Ship the specimen to the testing laboratory as soon as possible. It must be sent the same day it was collected.

6. Chain of custody must be strictly followed at every step, from collecting the specimen to reporting the test results, with sealed specimen containers, supervised laboratory analysis, and authorized signatures documented throughout.

Factors affecting results: Individual testing method results may vary. Some tests have lower limits of detection, which can make some results positive at lower substance levels. Also, a person’s diet, the volume of urine flow, and recent fluid intake can affect some results.

Patient coaching

Frequently, medical assistants are called on to explain specimen collection techniques to the patient. Patients want to do the procedure correctly but often lack knowledge of urinary terminology. They may be embarrassed or not know how to ask questions about cleaning the genital area. When explaining a urinary collection procedure, you should use pictures and words that the patient will understand. As you explain the procedure in terms the patient knows, he or she will feel comfortable telling you or asking you about pertinent details that may have a definite effect on treatment of the problem. Providing the patient with a clearly written instruction sheet also is helpful. The instruction sheet should be personalized with the patient’s name, the time to begin collecting or testing (if applicable), what supplies should be used, and a phone number to call if questions arise.

Legal and ethical issues

As the provider’s agent, you’re responsible for the validity of the specimen and procedure - collecting specimens correctly, testing them accurately, and strictly following protocol, especially when legal ramifications are involved. Patient confidentiality is paramount when drug testing is performed.

Patient-centered care

Urine testing is frequently done in an ambulatory care setting. Knowing laboratory procedures helps medical assistants to ask informed and useful questions of their patients. Vitamin C can affect urine reagent strip testing, so asking a patient if he or she takes a vitamin C supplement is useful for obtaining correct testing results. If a person consumes large amounts of vitamin C, a special strip can be used to detect interfering levels of vitamin C. If an elevated level is found, the patient should be instructed to discontinue vitamin C intake for 24 hours, and then another urine specimen should be collected for testing.

Professional behaviors

A laboratory professional performing urinalysis should have the following attributes:

• A discreet, respectful attitude with patients, co-workers, and supervisors.
• Sensitivity to patients’ concerns, reassuring them of test accuracy through therapeutic communication and, when needed, education.
• Good eyesight and manual dexterity.
• Accountability, honesty, and integrity when unsure of a procedure.
• Ability to multitask, manage time, and problem-solve if results are unexpected.