Sputum eosinophilia and NSBR can both be normal in challenge positive occupational asthma

Although there was a relationship between sputum eosinophilia, NSBR and occupatiuonal asthma both together and separately, the negative combination is not enough to exclude occupational asthma (negative predictive value 58% when compared with non-occupational asthma). There is no particular reason why NSBR or sputum eosinophilia should be diffeent in occupational and non-occupational asthma. If non-asthmatics are include the negative predictive value is higher. It shows that there are workers with challenge positive occupational asthma where both the NSBR and sputum eosinophils are normal when investigated a median 76 days after last exposure (Interquartile range 1 to 173, showing at least 25% were currently exposed at the time of the challenge). This is an interesting paper, but all the analysis is retrospective and requires prospective validation.

References

	Malo J-L, Cardinal S, Ghezzo H, LArchevêque J, Castellanos L, Maghni K, Association of bronchial reactivity to occupational agents with methacholine reactivity, sputum cells and immunoglobulin E-mediated reactivity, Clin Exp Allergy, 2011;41:497-504,

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