title: An inter-laboratory comparison of urinary 3-hydroxypropylmercapturic acid measurement demonstrates good reproducibility between laboratories.
abstract: BACKGROUND
  Biomarkers have been used extensively in clinical studies to assess toxicant exposure in smokers and non-smokers and have recently been used in the evaluation of novel tobacco products. The urinary metabolite 3-HPMA, a metabolite of the major tobacco smoke toxicity contributor acrolein, is one example of a biomarker used to measure exposure to tobacco smoke. A number of laboratories have developed liquid chromatography with tandem mass spectrometry (LC-MS/MS) based methods to measure urinary 3-HPMA; however, it is unclear to what extent the data obtained by these different laboratories are comparable.
  
  
  RESULTS
  This report describes an inter-laboratory comparison carried out to evaluate the comparability of 3-HPMA measurement between four laboratories. A common set of spiked and authentic smoker and non-smoker urine samples were used. Each laboratory used their in-house LC-MS/MS method and a common internal standard. A comparison of the repeatability ('r'), reproducibility ('R'), and coefficient of variation for 3-HPMA demonstrated that within-laboratory variation was consistently lower than between-laboratory variation. The average inter-laboratory coefficient of variation was 7% for fortified urine samples and 16.2% for authentic urine samples. Together, this represents an inter-laboratory variation of 12.2%.
  
  
  CONCLUSIONS
  The results from this first inter-laboratory comparison for the measurement of 3-HPMA in urine demonstrate a reasonably good consensus between laboratories. However, some consistent measurement biases were still observed between laboratories, suggesting that additional work may be required to further reduce the inter-laboratory coefficient of variation.
authors: British American Tobacco, Group Research and Development, Regents Park Road, Southampton, SO15 8TL, UK. emmanuel_minet@bat.com.
authors: Emmanuel
authors: E
authors: Minet
authors: Graham
authors: G
authors: Errington
authors: Gerhard
authors: G
authors: Scherer
authors: Kirk
authors: K
authors: Newland
authors: Mehran
authors: M
authors: Sharifi
authors: Brian
authors: B
authors: Bailey
authors: Mike
authors: M
authors: McEwan
authors: Francis
authors: F
authors: Cheung