title: Interference of tobacco smoke with immunochromatography assay for urinary drug detection.
abstract: BACKGROUND
  This study aimed to evaluate the interference of tobacco smoke on immunochromatography assay of urinary drug detection.
  
  
  METHODS
  Our study included 256 voluntary subjects (143 passive smokers and 113 current smokers). Cotinine was measured by immunoenzymatic method and thiocyanates (SCN(-)) by selective electrode. Urinary drug was detected by immunochromatography assay. A positive result is completed by an analytical method with an immunometric assay.
  
  
  RESULTS
  False positive results for benzodiazepines are significantly more frequent in smokers compared with passive smokers (90.2% Vs 22.4%; χ(2) = 116.62, p < 10(-3)). For smokers, the number of cigarettes was significantly higher in subjects with falsely positive results for benzodiazepines compared with subjects with negative results (32 ± 11 Vs 20 ± 10; p = 0.04). Between these two groups, we established a significant difference for urinary cotinine (345 ± 211 Vs 117 ± 54 μg/μmol; p < 10(-3)) and for plasma SCN(-) (101.6 ± 3.4 Vs 98.8 ± 2.1 μmol/L; p = 10(-3)). Urinary cotinine and consumption duration present the highest values of areas under curves (AUC) of the receiver-operating-characteristic (ROC) curves. The cut-off of 167.6 μg/μmol and 10.5 years were found as predictive factors of false positive results.
  
  
  CONCLUSIONS
  Tobacco smoke interferes with immunochromatography assay of urinary drug detection; therefore, all subjects must be questioned about their smoking status to avoid such false results during results interpretation.
authors.affiliation: Laboratory of Biochemistry-Toxicology, Monastir University Hospital, Monastir 5000, Tunisia. hajdhouha@yahoo.fr
authors.forename: Dhouha
authors.initials: D
authors.lastname: Haj Mouhamed
authors.forename: Asma
authors.initials: A
authors.lastname: Ezzaher
authors.forename: Hajer
authors.initials: H
authors.lastname: Mabrouk
authors.forename: Mohamed Hachem
authors.initials: MH
authors.lastname: Sâadaoui
authors.forename: Fadoua
authors.initials: F
authors.lastname: Neffati
authors.forename: Wahiba
authors.initials: W
authors.lastname: Douki
authors.forename: Lotfi
authors.initials: L
authors.lastname: Gaha
authors.forename: Mohamed Fadhel
authors.initials: MF
authors.lastname: Najjar
mesh_terms: D000328:Adult; D001569:Benzodiazepines / Q000652:urine*; D016022:Case-Control Studies; D002846:Chromatography, Affinity; D003367:Cotinine / Q000652:urine; D005189:False Positive Reactions; D053593:Forensic Toxicology; D006801:Humans; D012372:ROC Curve; D012907:Smoking / Q000009:adverse effects*; D015813:Substance Abuse Detection; D019966:Substance-Related Disorders / Q000175:diagnosis; D013861:Thiocyanates / Q000097:blood; D016482:Urinalysis
chemical_list: D013861:Thiocyanates; D001569:Benzodiazepines; D003367:Cotinine