Two phenotypes of occupational asthma separated by exhaled nitric oxide

Some workers with current exposure and occupational asthma have normal levels of exhaled nitric oxide, FeNO, (after controlling for inhaled corticosteroids and smoking, both of which reduce levels). This study showed that the normal FeNO group had less non-specific reactivity, but the same magnitude of PEF response to the occupational exposures as those with raised values. This is similar to the findings based on sputum eosinophilia. This helps explain the finding of normal non-specific reactivity in those with current exposure and occupational asthma. Whether the prognosis is related to phenotype  requires investigation. High and normal FeNO levels were seen in workers with high and low molecular weight sensitisation and do not seem to be related to the causative agent.

References

	Moore VC, Anees W, Jaakkola MS, Burge CB, Robertson AS, Burge PS, Two variants of occupational asthma separable by exhaled breath nitric oxide level, Respir Med, 2010;104:873-879,

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