The Truth About Toxicology Tests
WebMD Feature Archive
On television crime shows, the results of toxicology tests are spewed out at warp speed, sometimes available even before the autopsy is complete.
In real life, toxicology test results take much longer.
"Some of the tests take days, weeks, months," says Alan Hall, MD, a board-certified toxicologist and consultant in Laramie, Wyo. The final toxicology report, he says, draws not only from multiple test results and confirmation of the results, but also on the clinical experience of the toxicologists and pathologists involved in the investigation, as well as field work.
Here is what toxicology tests include, why they take so long, and why they can be tricky.
What is toxicology testing?
The toxicology testing performed after a person's death is known as forensic toxicology testing or postmortem drug testing.
That's different from clinical toxicology, according to the College of American Pathologists. This is the drug testing an emergency room doctor would be likely to order, for instance, if a patient shows up with signs and symptoms of drug overdose or abuse.
Other types of toxicology testing include workplace drug testing, which also screens for drugs of abuse, and athletic drug testing in sport programs, which detect banned substances or drugs that enhance performance.
The toxicology report that is eventually issued in forensic toxicology testing "is the result of the lab procedures identifying and quantifying potential toxins, which include prescription medications and drugs of abuse and interpretations of the findings," says Howard S. Robin, MD. He is the medical director of laboratory services at Sharp Memorial Hospital in San Diego and is a board-certified pathologist.
Toxicology testing is part of the autopsy report, Robin says. "A complete autopsy should have some level of toxicology studies."
How are forensic toxicology tests done?
At the time of the autopsy, collection of blood. urine, and tissue samples is done in preparation for the toxicology tests, says Barbarajean Magnani, PhD, MD, chairwoman of the Toxicology Resource committee for the College of American Pathologists. She is also vice-chair of the department of pathology and laboratory medicine at Tufts Medical Center, Boston.
"We collect blood from different areas, such as the femoral vein [in the leg] and heart blood," she tells WebMD. That's because the concentration of drugs can be different, she says, so comparing the concentrations can boost accuracy.
''We collect urine if there is any [in the body] and also use tissues [to test],” Magnani says.
Specimens taken for forensic toxicology testing routinely include, in addition to blood and urine, tissue samples from the liver. brain. kidney. and vitreous humor (the clear ''jelly" found in the eyeball chamber), according to information from the College of American Pathologists. Samples of the stomach contents and bile, a digestive juice secreted by the liver. are also collected routinely.
The tissue and fluid collection is typically done by a pathologist or morgue assistant, Robin says, and the process usually takes just 15 or 20 minutes.
Next, the specimens are turned over to a toxicology expert for testing. Testing is typically done by medical technologists or chemists, such as forensic chemists with doctoral training who are certified by The American Board of Clinical Chemistry or the American Board of Forensic Toxicology, according to the College of American Pathologists.
Medical examiner office personnel can also conduct toxicology drug testing related to an autopsy. Toxicology drug testing laboratories where the analyses are carried out are accredited by such organizations as the College of American Pathologists or state health departments or other organizations, to ensure uniform quality standards.
''The tissue is placed in special containers that prevent contamination of the tissue,'' Robin says. Preservatives can help prevent or delay breakdown of the drugs in the samples, Magnani says.
A ''paper trail'' records exactly who has handled the specimens to reduce the chance of contamination or mix-ups.
Just as important as the collection and tracking of fluid, blood, and tissue samples is the field investigation, Robin says. That involves officials looking into the medicine cabinet and around the home of the deceased person for drugs he or she may have been taking, including prescription drugs,
over-the-counter medicines, and illicit drugs.
That search could also turn up evidence that a person was getting prescriptions from several doctors.
Who interprets forensic toxicology tests, and how?
Toxicologists, chemists, and pathologists all need to be involved to correctly interpret results.
''The first thing we would do is a basic screen for drugs in the urine and in the blood," Magnani says. The search would be for drugs such as opiates, amphetamines. marijuana. alcohol, and barbiturates, she says.
The basic toxicology screen typically uses an immunoassay, Robin says. This type of test looks for drugs in the blood using specific antibodies that detect various classes of drugs.
If something shows up, a more sophisticated test is done, using techniques such as mass spectrometry, which can identify chemicals in substances by their mass and charge.
"These confirmatory methods are actually more sensitive," Robin says. "You can find lower quantities [of the substance]."
The more sophisticated tests can tell experts the exact concentration of the drug or other substance, says Hall, who is also clinical assistant professor of public health at Weatherford College in Weatherford, Texas.
Experts also can determine if two drugs found together may have had a synergistic effect -- which happens when two drugs similar in their actions produce an exaggerated effect when taken together. It's akin to ''one plus one equals five," Robins says.
Experts have to determine if the drug or other substances found in the specimens are a therapeutic dose, a toxic dose, or a lethal dose -- whether they contributed to the death or caused the death.
Why do the forensic toxicology tests take so long?
Getting a complete and accurate forensic toxicology test result can be a lengthy process for a variety of reasons, according to the College of American Pathologists and experts interviewed by WebMD.
There may be a lot of specimens that need to be tested, which means more testing time. And as an investigation proceeds, information about the possibility of another drug being involved may surface, so even more testing may be needed.
When the first round of positive tests have to be confirmed by the more sophisticated method, this may require sending out the specimens to more specialized laboratories. And that adds to the delay.
"Four to six weeks is pretty standard," Magnani says of the time line for forensic toxicology testing. Besides the time needed for painstaking analysis and confirmation, she says, there could be a backlog of tests that need to be done at a particular laboratory.
"Each one should be handled thoroughly, whether they are a celebrity or not," she says.
How do the toxicology reports help determine cause of death?
Experts look to see if the concentration of drugs or poisons are in the toxic or lethal range, Magnani says. They take into account other information, such as symptoms before their death.
For instance, she recalls a man who passed out and when roused by police was so belligerent it took several officers to subdue him. Then he died suddenly.
No physical findings from the autopsy pointed to a cause of death, she says. ''The toxicology report showed the presence of cocaine at a level sufficient to cause death," she says. And the belligerent behavior was another clue.
But not every toxicology report is so clear-cut, Robin says. And television really does present a skewed view of forensic toxicology testing, he and other experts agree.
"At the end of the [TV crime] show, they don't say it's an indeterminate cause of death," he says. But in real life? "Two to five percent of deaths are indeterminate," Robin says, citing forensic literature.
What complicates the process? Drugs of abuse can change constantly, Robin says, with one drug becoming popular, for instance, while others fade in popularity. "You are always looking for what is the new drug [of choice]," he says.
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Howard S. Robin, MD, medical director of laboratory services, Sharp Memorial Hospital, San Diego.
Barbarajean Magnani, PhD, MD, chairwoman, toxicology resource committee, College of American Pathologists, Northfield, Il.; chief of clinical pathology and vice chairwoman, Tufts Medical Center, Boston.