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Which low molecular weight chemicals potentially cause allergy?

Posted Feb 24 2010 8:13am

Until now there is no agreed protocol for the prediction of low molecular weight (LMW) respiratory sensitizers. To assess the validaty of a previously published quantitative structure–activity relationship (QSAR) model for the prediction of novel chemical respiratory sensitizers research was done on already known asthmagenic (28) and control chemicals (129). 

The area under the receiver operating characteristic (ROC) curve for the model’s ability to distinguish asthmagens from controls was 0.87 (95% CI 0.76–0.97). With a cut-off hazard index of 0.5 resulting in sensitivity of 79% and specificity of 93%.  The ROC curve for this QSAR demonstrates good global predictive power for distinguishing asthmagenic from non-asthmagenic LMW organic compounds. This makes QSAT potentially useful for occupational and respiratory physicians.

Further validation of computer-based prediction of chemical asthma hazard
 Seed, M., Agius, R. Occupational Medicine 2010 60(2):115-120

Background: There is no agreed protocol for the prediction of low molecular weight (LMW) respiratory sensitizers. This creates challenges for occupational physicians responsible for the health of workforces using novel chemicals and respiratory physicians investigating cases of occupational asthma caused by novel asthmagens.

Aims:  To iterate the external validation of a previously published quantitative structure–activity relationship (QSAR) model for the prediction of novel chemical respiratory sensitizers and to better characterize its predictive accuracy.

Methods: An external validation set of control chemicals was identified from the Australian Hazardous Substances Information System. An external validation set of asthmagenic chemicals was identified by a thorough search of the peer-reviewed literature from January 1995 onwards using the Medline database. The QSAR model was used to determine an ‘asthma hazard index’ (between 0 and 1) for each chemical.

Results: A total of 28 external validation asthmagens and 129 control chemicals were identified. The area under the receiver operating characteristic (ROC) curve for the model’s ability to distinguish asthmagens from controls was 0.87 (95% CI 0.76–0.97). Using a cut-off hazard index of 0.5 resulted in sensitivity of 79% and specificity of 93%. For prior probability ranging from 1:300 to 1:100, the negative predictive value (NPV) was 1 and positive predictive value (PPV) 0.04–0.1 while for prior probability ranging from 1:20 to 1:3, the NPV was 0.91–0.99 and PPV 0.39–0.85.

Conclusions: The ROC curve for this QSAR demonstrates good global predictive power for distinguishing asthmagenic from non-asthmagenic LMW organic compounds. Potential for utilization by occupational and respiratory physicians is evident from its predictive values.


Filed under: Asthma , Chemical agents , New occupational risks Tagged: Allergy , Asthma , Chemicals
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