Indications for Testing
Testing is appropriate when it is necessary to evaluate individuals for recent use of nicotine-containing products or passive exposure to nicotine. It can also be used to document use of tobacco versus purified nicotine products when assessing compliance with smoking cessation programs or to verify abstinence from nicotine-containing products when qualifying patients for surgery or organ transplant.
Urine testing is recommended over serum or plasma testing to detect chronic use because analytes are detectable for a longer period of time in urine than in serum or plasma. The trans-3'-hydroxycotinine metabolite may persist for weeks after cessation of long-term or heavy use of nicotine products. Urine metabolite testing is also recommended for determining active or passive exposure, although testing cannot discriminate the two definitively. Anabasine, a tobacco alkaloid, can also be detected in urine and may distinguish the active use of tobacco products from nicotine replacement therapy; individuals using purified nicotine products would not be expected to have anabasine in urine. Because nicotine can be found in varying amounts in several vegetables, including cauliflower, eggplant, tomatoes, and potatoes, and in some teas, consumption of such vegetables may explain the presence of nicotine and its metabolite cotinine in the urine of nonsmokers. A cutoff of 100 ng/mL cotinine is frequently used for surgery qualification purposes.
Serum or Plasma
Serum or plasma testing may be required when a valid urine specimen cannot be obtained, for example, from anuretic patients or those on dialysis. Serum or plasma testing can detect recent use, typically within the past 2 weeks, and is more closely correlated with oral fluid testing than with urine testing. Serum or plasma testing by quantitative liquid chromatography-tandem mass spectrometry cannot distinguish between use of tobacco and purified nicotine products. A cutoff of 10 ng/mL cotinine is frequently used for surgery qualification purposes. See also the Emergency Toxicology topic.
The cotinine qualitative screen is recommended to assess active exposure to nicotine and to document abstinence from nicotine-containing products for compliance with smoking-cessation programs or for surgery qualification. It does not determine passive use nor differentiate between tobacco use and nicotine replacement therapy; for such results, quantitative urine testing is preferred.