Baby Wash Triggers False Positive Tests In Drug-Free Babies

by Heidi Green
June 26, 2012

Baby’s “first bath” is an innocent rite of passage for many newborns. But if the bath involves any of several commonly used cleansing products, baby’s “first bath” may become “baby’s first positive drug screening test.” It seems surreal— researchers themselves are calling this conclusion “unexpected”—but that’s the finding of a recent study.

Research
Although the U.S. Preventive Services Task Force states that “current evidence is insufficient to assess the balance of benefits and harms of screening … pregnant women,” many health care providers do rely on a combination of maternal interview and lab tests to identify drug exposure in newborns. The most common form of testing analyzes levels of tetrahydrocannabinol (known as THC, this is the active ingredient found in marijuana) in the urine of a mother and/or her infant. (Infant’s meconium—the tarry black stools passed the first day or two after birth—can also be tested.) These tests are used because they are cost-effective, easy to administer, and provide quick results.

Lab standards vary, but a measure of 20 to 50 ng/mL is considered positive for marijuana. The test should be used for screening purposes only. Those with positive test results should be reevaluated using more sensitive and specific techniques. Unfortunately, many clinical labs lack the equipment to do so. Often, positive screening results are accepted as-is, no retesting is done, and clinical—and legal—action is taken based on these results.

Researchers at the University of North Carolina initiated this study to determine the cause of possible “false positive” test results at their facility. In April 2011, the hospital issued a new recommendation for drug testing of newborns born to mothers who had minimal prenatal care. Initially, the number of positive results at the hospital increased due to more testing (10 to 40 percent of babies born in the hospital receive the test in any given month). However, in July, three infants had positive urine drug tests while their meconium tested negative.

The mothers’ and newborns’ drug histories were reviewed, but no known cross-reacting agents were identified. Positive samples were sent for further testing, while laboratory staff and clinicians discussed testing procedures. The researchers found wide variation between nursing staff practices. For example, only some staff cleansed the newborns before collecting a sample; and some placed cotton balls or gauze within the diaper to collect the sample, while others used collection devices. The researchers decided to take a closer look at what was happening in the hospital nursery that might be creating false positive urine drug tests.

The researchers looked at products routinely used in the nursery, as well as similar products, including Head-to-Toe Foaming Wash and Johnson’s Bedtime Bath (both from Johnson & Johnson), CVS Night-Time Baby Bath and CVS Baby Shampoo, Aveeno Soothing Relief Creamy Wash, and Aveeno Wash Shampoo. They also looked at other products newborns have contact with, including Medichoice Baby Wipes, Kendall Curity Gauze Sponge, Huggies Newborn Diapers, Huggies Preemie Diapers, U-Bag urine collection bags, and cotton balls and a brand of hygienic cleaning towelettes used by hospital staff.

The researchers mixed drug-free urine with these materials and substances, then tested them in the laboratory using the standard screening methods.

Results
None of the materials—cotton balls, diapers, wipes, or urine collection kits—resulted in positive tests. The baby washes were another story.

Drug-free urine mixed with Head-to-Toe Baby Wash led to positive tests, even when very small amounts were used. Just 0.1 mL of wash led to a positive test. This relationship was dose-dependent; that is, the more baby wash that was added, the higher the “THC” value.

But this result wasn’t isolated to Head-to-Toe Baby Wash. According to the researchers, “all additional soap products tested were found to cause some level of reactivity” with the drug test, except for the hospital foaming hand soap. In fact, the majority of the washes—Head-to-Toe Baby Wash, Johnson & Johnson Bedtime Bath, CVS Night-Time Baby Bath, Aveeno Soothing Relief Creamy Wash, and Aveeno Wash Shampoo—reacted strongly enough to cause false positive tests.

Although the soaps themselves do not include THC, the false positives occur when residual soap on the skin makes its way into the baby’s urine sample.

Recommendations
“The results of newborn drug screening have far-reaching impact not only in health care, but also in the legal domain,” study researchers explain in the article. “Therefore, the accuracy of these results cannot be undervalued.” Positive results typically lead to involvement of social services or false child abuse allegations.

The findings of this study suggest:

• Infants should be bathed with water-only during their hospital stay.
• Health care providers should be aware of this potential source of false positive screening results, and consider additional testing to confirm positive results before intervening.
• Parents should be aware of this potential source of false positive screening tests.
• If baby wash is to be used during the newborn bath, infants could be screened before their first bath.

It is important to note that babies do not need to be bathed in anything but water in their early days and weeks. A soft, damp washcloth is really all that is needed to clean a newborn head to toe. For more on bathing your baby once you return home from the hospital, read “Splish, Splash, Baby’s Bath.”