Abstract

PURPOSE:
Increases of fractional exhaled nitric oxide (FeNO), sputum eosinophils, and methacholine responsiveness have been described after specific inhalation challenges (SIC) with occupational allergens, but limited information is available about their comparative performance. It was the aim of the study to assess the diagnostic accuracy of these non-invasive tests before and after SIC for the diagnosis of occupational asthma (OA).

METHODS:
A total of 122 subjects with work-related shortness of breath were included. The 'gold standard' was defined as airway obstruction (pulmonary responders) and/or an increase of FeNO of at least 13 ppb after SIC. The results were compared with those obtained using the pulmonary responder status alone as 'gold standard'.

RESULTS:
If the pulmonary responder status and/or an increase of FeNO was used as 'gold standard' for SIC, 28 out of 39 positives (72%), but also 20 out of 83 negatives (24%) showed an increase of sputum eosinophils and/or bronchial hyperresponsiveness after SIC. If the pulmonary responder status alone was used as 'gold standard', an increase of FeNO with a sensitivity of 0.57 and a specificity of 0.82 showed a higher accuracy than increases of sputum eosinophils (0.52/0.75) or bronchial hyperresponsiveness (0.43/0.87). Individual case analyses suggest that a few cases of OA may be detected by increases of sputum eosinophils or bronchial hyperresponsiveness alone, but probably false-positive tests dominate.

CONCLUSION:
It is recommended to use both lung function and increase of FeNO as primary effect parameters of SIC. Changes of sputum eosinophils and bronchial hyperresponsiveness after SIC have a low additional diagnostic value, but may be useful in individual cases.

Full Text

Comments

This is a report of SIC for occupational asthma from the Bochum centre where workers with suspected occupational asthma are referred by insurance companies and courts for a diagnosis of occupational asthma. There is a single active challenge day with cumulative exposures and a 4 hour follow-up only, with no independent diagnosis apart from occasional FeNO measurements at work. A positive SIC was defined as a >20% fall in FEV1 from baseline with a significant increase in specific resistance, this was seen in 21/122 workers. An additional 18 were classed as positive as defined by a FENO increase of >13ppb. This is a difficult study from which to make generalisations due to the single agent tested on a single day, restricted monitoring post SIC, the criteria for a positive SIC and a lack of independent methods of diagnosis. The authors conclude that an increase in sputum eosinophils and/or NSBR was seen in 72% of those with a positive SIC and 24% with a negative SIC, and had low additional diagnostic value.

6/26/2019