Occupational Asthma Reference
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Lemiere C, D'Alpaos V, Chaboillez S, Cesar M, Wattiez M, Chiry S, Vandenplas O,
Investigation of occupational asthma: sputum cell counts or exhaled nitric oxide?.,
Chest,
2010;137:617-622,
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Keywords: Canada, Belgium, induced sputum, nitric oxide, challenge
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Abstract
BACKGROUND
The measure of sputum eosinophil counts is a useful tool in the investigation of occupational asthma (OA), but processing sputum is time consuming. Measuring the fractional concentration of exhaled nitric oxide (FENO) may be an alternative in clinical practice. The aim of this study was to assess the respective changes of sputum eosinophil counts and FENO following exposure to occupational agents in the routine practice of two tertiary centers in North America and Europe.
METHODS
Workers undergoing specific inhalation challenges (SICs) for possible OA in tertiary clinics in both Canada and Belgium were enrolled. Sputum cell counts and FENO were collected at the end of the control day and at 7 and 24 h after exposure to the offending agent.
RESULTS
Forty-one subjects had a negative SIC; 26 subjects had OA proven by a positive SIC. In subjects with positive SIC, there was a significant increase in sputum eosinophils at 7 h (9.0 [9.9]%) and 24 h (11.9 [14.9]%) after exposure compared with the baseline (2.8 [4.2]%), whereas there was a significant increase in FENO only 24 h after exposure (26.0 [30.5] ppb) compared with the baseline (16.6 [18.5] ppb). A 2.2% change in sputum eosinophil counts achieved a much higher sensitivity and positive predictive value than a 10-ppb change in FENO with similar specificity and negative predictive value for predicting a 20% decrease in FEV(1) during SICs.
CONCLUSIONS
Sputum eosinophil counts constitute a more reliable tool than FENO to discriminate positive and negative SICs.
Full Text
Comments
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Induced sputum and FeNO measured before, at 7 and 24 hours after specific challenge.A 2.2% increase in sputum eosinophils post challenge had a sensitivity 74-79 % (at 7 and 24 hours) and a specificity of 81% aginst specific challenge in 20 challenge positive and 16 challenge negative subjects (post hoc analysis). FeNO showed no significant change at 7 hours, an increase >10ppb at 24 hours had a sensitivity of 37% for a specificity of 81%. The next stage would be to test the 2.2% increase in eosinophils is subjects whose challenges were equivical in terms of FEV1 decline, or who showed a <20% FEV1 fall post challenge. The mean FEV1 fall in this group was high at 30% (SD 11.45). 14/26 had immediate reactions aline.
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