title: Unexpected interference of baby wash products with a cannabinoid (THC) immunoassay.
abstract: OBJECTIVE
  The results of newborn drug screening have far-reaching impact not only in healthcare, but also in the legal domain. Therefore, the accuracy of these results cannot be undervalued. When false positive cannabinoid (THC) screening results for this population were suspected at our institution, a multidisciplinary approach was initiated to evaluate the screening process for any pre-analytical or analytical sources of error or interference.
  
  
  METHODS
  Mixtures of drug-free urine with various commercial products and materials that commonly contact newborns in our nursery were prepared and tested using the immunoassay screening methods in our laboratory. Additional commercial products were similarly tested; and when available, individual surfactants common to the interfering products were also evaluated.
  
  
  RESULTS
  Addition of Head-to-Toe Baby Wash to drug-free urine produced a dose dependent measureable response in the THC immunoassay. Addition of other commercially available baby soaps gave similar results, and subsequent testing identified specific chemical surfactants that reacted with the THC immunoassay.
  
  
  CONCLUSIONS
  We have identified commonly used soap and wash products used for newborn and infant care as potential causes of false positive THC screening results. Such results in this population can lead to involvement by social services or false child abuse allegations. 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. Most importantly, we demonstrate the need for active involvement in the "total testing process," as sources of error are not confined to the laboratory walls.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina - Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Cotten
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Duncan
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Burch
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Seashore
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Hammett-Stabler
mesh_terms: D013759:Dronabinol / Q000652:urine*; D005189:False Positive Reactions; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007231:Infant, Newborn; D015997:Neonatal Screening; D011619:Psychotropic Drugs / Q000652:urine*; D012915:Soaps / Q000032:analysis*; D015813:Substance Abuse Detection / Q000379:methods / Q000592:standards*
chemical_list: D011619:Psychotropic Drugs; D012915:Soaps; D013759:Dronabinol