The science is alarmingly inconclusive, but the punishment for mothers is severe.
November 23, 2012 |
Employees at US hospitals are testing more and more newborns for cannabis exposure. And, with alarming frequency, they are getting the wrong results. So say a pair of recent studies documenting the unreliability of infant drug testing.
In the most recent trial, published in the September edition of the Journal of Clinical Chemistry , investigators at the University of Utah School of Medicine evaluated the rate of unconfirmed "positive" immunoassay test results in infant and non-infant urine samples over a 52-week period. Shockingly, authors found 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 specimens as 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 testing – the standard technology used in workplace drug testing – relies on the use of antibodies (proteins that will react to a particular substance or a group of very similar substances) to 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 known as false positives.
False positive test results for cannabis’ carboxy THC metabolite are relatively uncommon in adult specimens. Among newborns’ specimens, however, false positive results for alleged cannabis exposure are disturbingly prevalent.
In April, researchers at the University of North Carolina reported in the journal Clinical Biochemistry that various chemicals present in various baby wash products, such as 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.
“[The] addition of Head-to-Toe Baby Wash to drug-free urine produced a dose dependent measureable response in the THC immunoassay,” the investigators concluded . “Addition of other commercially available baby soaps gave similar results, and subsequent testing identified specific chemical surfactants that reacted with the THC immunoassay. … Given these consequences, it is important for laboratories and providers to be aware of this potential source for false positive screening results and to consider confirmation before initiating interventions.”
Following the publication of the UNC study, researchers at the University of Utah screened for the presence of baby soap contaminants in infant urine. Surprisingly, they didn’t find any . Rather, they concluded that the disproportionately high rate of false positive test results discovered among their samples were the result of a cross-reaction with some other yet-to-be determined constituent. They cautioned: “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.”
Yet despite these warnings, in many instances, hospitals fail to confirm the results of presumptive drug tests prior to reporting them to state authorities. (Because confirmatory testing is more expensive the immunoassay testing, many hospitals neglect to send such presumptive positive urine samples to outside labs for follow-up analysis.) Ironically, such confirmatory tests are required for all hospital employees who test positive for illicit substances. But presently, no such guidelines stipulate that similar precautions be taken for newborns or pregnant mothers. Explains Lynn Paltrow, executive director of National Advocates for Pregnant Women : “NAPW has had calls from numerous parents who were subjected to intrusive, threatening, and counterproductive child welfare interventions based on false or innocent positive test results for marijuana. We have learned that pregnant patients receive fewer guarantees of accuracy than do job applicants at that same hospital.”
Regardless of whether or not the drug screen results are confirmed, the sanctions for those subjects who test positive are often swift and severe. Typically, any report of alleged infant exposure to cannabis will trigger a host of serious consequences ranging from the involvement of social services to accusations of child endangerment or neglect. In some instances, mothers whose infants test positive for carboxy THC will lose temporary child custody rights and be mandated to attend a drug treatment program. In other instances they may be civilly prosecuted. At least 18 states address the issue of pregnant women’s drug use in their civil child neglect laws; in 12 states prenatal exposure to any illegal drug is defined by statute as civil child abuse. (One state, South Carolina, authorizes the criminal prosecution of mothers who are alleged to have consumed cannabis, or any other illicit substance, during pregnancy and carry their baby to term.)
Of further concern is the reality that the hospital staff’s decision to drug test infants or pregnant mothers appears to be largely a subjective one. There are no national standards delineating specific criteria for the drug testing of pregnant women, new mothers, or their infants. In fact, the only federal government panel ever convened to advise on the practice urged against its adoption. As a result, race and class largely influence who is tested and who isn’t. A 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. A separate study published in the New England Journal of Medicine reported similar rates of illicit drug consumption during pregnancy among both black and white women, but found that “black women were reported [to health authorities] at approximately 10 times the rate for white women.”
How many mothers have been accused of child neglect or abuse because of false positive drug test results? Nobody knows for sure. But no doubt some mothers have been penalized solely as a result of the test’s inherent fallibility – and many more are likely to face similar sanctions in the future. That’s because the practice of drug testing infants for cannabis exposure remains a relatively popular even though there exists limited, if any, evidence to justify it.
“No child-health expert would characterize recreational drug use during pregnancy as a good idea,” writes Time.com columnist Maia Szalavitz. “But it’s not at all clear that the benefits, if any, of newborn marijuana screening – particularly given how selectively the tests are administered – justify the potential harm it can cause to families.”
Richard Wexler, executive director of the National Coalition for Child Protection Reform agrees, telling Time.com that the emotional damage caused by removing an infant child from their mothers, as well as the risk of abuse inherent to foster care, far outweigh any risks to the child that may be caused by maternal marijuana use during pregnancy.
In fact, the potential health effects of maternal marijuana use on infant birth weight and early development have been subject to scientific scrutiny for several decades. One of the earliest and most often cited studies on the topic comes from Dr. Melanie Dreher and colleagues, who assessed neonatal outcomes in Jamaica, where it is customary for many women to ingest cannabis, often in tea, during pregnancy to combat symptoms of morning sickness. Writing in the journal Pediatrics in 1994, Dreher and colleagues reported no significant physical or psychological differences in newborns of heavy marijuana-using mothers at three days old, and found that exposed children performed better on a variety of physiological and autonomic tests than non-exposed children at 30 days. (This latter trend was suggested to have been a result of the socio-economic status of the mothers rather than a result of pre-natal pot exposure.)
Separate population studies have reported similar results. A 2002 survey of 12,060 British women reported, “[C]annabis use during pregnancy was unrelated to risk of perinatal death or need for special care.” Researchers added that “frequent or regular use” of cannabis throughout pregnancy may be associated with “small but statistically detectable decrements in birthweight.” However, the association between cannabis use and birthweight failed to be statistically significant after investigators adjusted for confounding factors such as the mothers’ age, pre-pregnancy weight, and the self-reported use of tobacco, alcohol, caffeine, and other illicit drugs.”