Salt Lake City, UT–(ENEWSPF)–August 23, 2012. False positive drug test results for cannabis are far more common to occur in infant urine samples than in those provided by non-infants, according to a study published online in the journal Clinical Chemistry.
Researchers at the University of Utah School of Medicine and ARUP drug testing laboratories in Salt Lake City investigated the rate of unconfirmed ‘positive’ immunoassay test results in infant and non-infant urine samples over a 52-week period.
Authors reported that positive tests for carboxy THC, a byproduct of THC screened for in immunoassay urine tests, were 59 times less likely to be confirmed in infant urine compared to non-infant urine samples. Overall, 47 percent of the infant ‘positive’ immunoassay urine samples evaluated did not test for the presence of carboxy THC when confirmatory assay measures were later performed.
Immunoassay tests rely on the use of antibodies (proteins that will react to a particular substance or a group of very similar substances) and document whether a specific reaction occurs. Therefore, a ‘positive’ result on an immunoassay test presumes that a certain quantity of a particular substance may be present in the sample, but it does not actually identify the presence of the substance itself. A more specific chemical test, known as chromatography, must be performed in order to confirm any preliminary analytical test results. Samples that test positive on the presumptive immunoassay test, but then later test negative on the confirmatory test are know as false positives.
In April, researchers at the University of North Carolina reported that chemicals present in various baby wash products, including Johnson’s Head-to-Toe Baby Wash and CVS Baby Wash, frequently cross-react with the immunoassay test to cause ‘false positive’ results for carboxy THC. However, in this latest study, none of the unconfirmed immunoassay test results were due to contaminants from baby wash soaps.
Researchers concluded: “Until the compounds contributing to positive urine screen results in infants are identified, we encourage the use of alternative specimens for the detection and investigation of neonatal exposure to cannabinoids. Screen-positive cannabinoid results from infant samples should not be reported without confirmation or appropriate consultation, because they cannot currently be interpreted.”
Infants may be drug tested in situations where their mothers are suspected of consuming illicit substances during pregnancy or have tested positive for illicit substances themselves. However, critics of infant drug testing argue that the hospital staff’s decision regarding whether to conduct such tests is often subjective and potentially discriminatory. For example, a 2007 study published in the Journal of Women’s Health reported that “black women and their newborns were 1.5 times more likely to be tested for illicit drugs as non-black women,” after controlling for obstetrical conditions and socio-demographic factors, such as single marital status or a lack of health insurance.
Twelve states legally define prenatal exposure to any illegal drug as child abuse.
Full text of the study, “Unresolved discrepancies between cannabinoid test results for infant urine,” appears in the journal Clinical Chemistry.