Up to 70 percent of drug tests on newborns falsely come up positive for the presence of methamphetamine, and other routine drug tests are often wrong, as well, experts say.

The Los Angeles Daily News reported June 28 that testing of meconium samples -- the first stool produced by a newborn -- is frequently incorrect, according to Brown University's Barry Lester. Experts recommend that hospitals testing for maternal drug use conduct confirmatory or forensic testing to verify results, but many hospitals don't do so.

"It's not the hospital's burden to do a confirmatory test," said James Lott, executive vice president of the Hospital Association of Southern California. "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."

False positive results on drug tests can be caused by a variety of factors, including use of cold medicines or even consumption of poppy seeds. Research suggests that tests for methamphetamine are incorrect 26 percent of the time, on average, while tests for opiates are wrong in 29 percent of cases, according to a study in the January 2008 issue of the Mayo Clinic Proceedings.