Pubdate: Sat, 28 Jun 2008
Source: Los Angeles Daily News (CA)
Copyright: 2008 Los Angeles Newspaper Group
Author: Troy Anderson


Up to 70 Percent of Initial Checks Can Be Wrong

Hospitals' initial urine-screening drug tests on pregnant women can
produce a high rate of false positives - particularly for
methamphetamine and opiates - because they are technically complex and
interpretation of the results can be difficult, some experts say.

Tests for methamphetamine are wrong an average of 26 percent - and
possibly up to 70 percent - of the time, according to studies by the
University of Kansas Medical Center, U.S. Substance Abuse and Mental
Health Services Administration and the American Association for
Clinical Chemistry.

And even the gold standard of maternal drug testing - meconium, a
baby's first stool that is analyzed to assess a mother's drug usage
over the past four or five months - can produce false positives for
methamphetamine up to 70 percent of the time, said Dr. Barry Lester, a
national expert on drug-exposed babies and a professor of pediatrics
and psychiatry at Brown University in Providence, R.I. False positives
can be triggered by everything from cold medicines and diet pills to
poppy seeds, according to a January study by the University of Kansas
published in Mayo Clinic Proceedings.

The study found cold remedy compounds, herbal medications and
doctor-prescribed medicines for anxiety or depression often produce
false positives for methamphetamines.

On average, the study found initial urine screens for methamphetamines
produced false positives 26 percent of the time. For opiates, the
percentage rose to 29 percent. Less than 8 percent of tests for
cocaine and marijuana resulted in false positives.

"There is a relatively good chance that there will be a false positive
for those particular drugs (methamphetamine and opiates)," said Dr.
Donald Frederick, chairman of the toxicology division at the American
Association of Chemistry in Washington, D.C.

"I always recommend they go to confirmatory or forensic testing if
they are going to use any clinical immunoassays for legal purposes."

Hospital doctors have the discretion whether to request an initial
urine screen and usually do so only if the mother exhibits signs of
drug use, the baby is born premature or underweight, or other reasons

If a test is positive, many hospitals perform confirmatory tests to
ensure the results are accurate - but some don't.

The U.S. Substance Abuse and Mental Health Services Administration
said the federal government has required confirmatory tests for its
employees since 1988 to help eliminate false positives.

Confirmatory tests usually involve gas chromatography and mass

But James Lott, executive vice president of the Hospital Association
of Southern California, said it's not the hospital's responsibility to
conduct confirmatory drug tests.

"It's not the hospital's burden to do a confirmatory test," Lott said.
"It's up to the agency that investigates child abuse whether a
confirmatory test needs to be done.

"The hospital can choose to do it if it wants to, but it's not
obligated to do it." 
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