While infant drug tests are commonly used across the United States, it’s often done only in cases where the mother has some history of substance use, reports Stephen C. Webster at The Raw Story. Positive results for marijuana on the immunoassay drug test are often followed by a more targeted THC test to confirm the results.
But scientists with the University of Utah found that even the more targeted THC assay tests — the ones used for confirming results — show a “significantly higher” rate of false-positive results with infants.
Research published in 2012 found that many different soaps and household products, including baby shampoo, can cause false positives in immunoassay tests. This follow-up study tried to determine what’s behind the higher rates of false positives for infants.
The study doesn’t even touch the subject of whether non-pot-smoking parents have unjustly lost custody of their babies due to false positive drug test results. But it does greatly damage the view that THC assay testing is a reliable method of detecting cannabis use.
According to the researchers, infant urine analysis results that show positive for marijuana “should not be reported without confirmation [from an alternate specimen] or appropriate consultation, because they cannot currently be interpreted.”
“Positive THC screening results may thus reflect compounds other than cannabinoids that are present in the urine of infants at high risk of drug exposure, or they may reflect environmental or socioeconomic factors associated with their high-risk situations,” the researchers speculated.
The scientists who found the original flaw in immunoassay testing said two compounds in particular were responsible for causing false positives: polyquaternium 11 and cocamidropropyl betaine, which, according to the U.S. Department of Health and Human Services, are in hundreds of household products like Windex, Lime-A-Way, Axe shower gel, Clairol hair coloring, Dial foaming hand soap, Crest toothpaste, a number of baby shampoos and others.
They discovered that less than 0.1 milliliter of these substances in a urine sample could contaminate the results, causing a false positive.
The University of Utah scientists originally wanted to determine why infant drug testing had false positives more often. But it turns out they couldn’t explain the difference.
They just called the issue “unresolved” and said “more study” was needed to explain the false positives, leaving innocent parents in the lurch in the meantime. The researchers also speculated that infants might metabolize THC differently than adults due to underdeveloped liver enzymes.
“It would be helpful if future studies identified THC metabolites with prospectively collected infant urine samples matched for hospital location, used the same sample-collection protocols, and stratified the infants according to the risk of drug exposure,” the scientists wrote.