title: A refined QSAR model for prediction of chemical asthma hazard.
abstract: BACKGROUND
  A previously developed quantitative structure-activity relationship (QSAR) model has been extern ally validated as a good predictor of chemical asthma hazard (sensitivity: 79-86%, specificity: 93-99%).
  
  
  OBJECTIVE
  To develop and validate a second version of this model.
  
  
  METHODS
  Learning dataset asthmagenic chemicals with molecular weight (MW) <1 kDa were identified from reports published in the peer-reviewed literature before the end of 2012. Control chemicals for which no reported case(s) of occupational asthma had been identified were selected at random from UK and US occupational exposure limit tables. MW banding was used in an attempt to categorically match the control group for MW distribution of the asthmagens. About 10% of chemicals in each MW category were excluded for use as an external validation set. An independent researcher utilized a logistic regression approach to compare the molecular descriptors present in asthmagens and controls. The resulting equation generated a hazard index (HI), with a value between zero and one, as an estimate of the probability that the chemical had asthmagenic potential. The HI was determined for each compound in the external validation set.
  
  
  RESULTS
  The model development sets comprised 99 chemical asthmagens and 204 controls. The external validation showed that using a cut-point HI of 0.39, 9/10 asthmagenic (sensitivity: 90%) and 23/24 non-asthmagenic (specificity: 96%) compounds were correctly predicted. The new QSAR model showed a better receiver operating characteristic plot than the original.
  
  
  CONCLUSIONS
  QSAR refinement by iteration has resulted in an improved model for the prediction of chemical asthma hazard.
authors.affiliation: Department of Information Services, The University of Edinburgh, Edinburgh EH8 9LJ, UK.
authors.forename: J
authors.initials: J
authors.lastname: Jarvis
authors.affiliation: Centre for Occupational and Environmental Health, Centre for Epidemiology, Institute of Population Health, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PL, UK. martin.seed@manchester.ac.uk.
authors.forename: M J
authors.initials: MJ
authors.lastname: Seed
authors.affiliation: Centre for Occupational and Environmental Health, Centre for Epidemiology, Institute of Population Health, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Stocks
authors.affiliation: Centre for Occupational and Environmental Health, Centre for Epidemiology, Institute of Population Health, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Agius
mesh_terms: D059366:Asthma, Occupational / Q000453:epidemiology / Q000517:prevention & control*; D015386:Hazardous Substances / Q000009:adverse effects*; D006801:Humans; D008962:Models, Theoretical; D008970:Molecular Weight; D009784:Occupational Diseases / Q000139:chemically induced / Q000453:epidemiology / Q000517:prevention & control*; D016273:Occupational Exposure / Q000009:adverse effects* / Q000517:prevention & control; D009930:Organic Chemicals / Q000009:adverse effects*; D012372:ROC Curve; D018570:Risk Assessment
chemical_list: D015386:Hazardous Substances; D009930:Organic Chemicals
keywords: Occupational asthma; occupational chemicals; toxicology.