Assessment of eosinophilic airway inflammation as a contribution to the diagnosis of occupational asthma

• Published in: Allergy (Copenhagen) 2018-01, Vol.73 (1), p.206-213
• Main Authors: Beretta, C., Rifflart, C., Evrard, G., Jamart, J., Thimpont, J., Vandenplas, O.
• Format: Article
• Language: English
• Subjects: Asthma; bronchial provocation tests; Diagnosis; eosinophils; Histamine; Inhalation; Leukocytes (eosinophilic); Medical diagnosis; Nitric oxide; Occupational diseases; Respiration; Respiratory tract; Respiratory tract diseases; Sensitivity; Sputum
• ISSN: 0105-4538; 1398-9995
• DOI: 10.1111/all.13265

Background Ascertaining the presence of asthma through the assessment of nonspecific bronchial hyperresponsiveness (NSBH) is a key step in the diagnosis of occupational asthma (OA). We aimed at investigating whether indices of airway inflammation including fractional exhaled nitric oxide (FeNO) and sputum eosinophils would be useful adjuncts to the measurement of NSBH in diagnosing OA defined as a positive specific inhalation challenge (SIC). Methods The study included 240 consecutive subjects with a suspicion of OA who completed a SIC, of whom 133 showed a positive response. The sensitivity, specificity, and predictive values of NSBH, and FeNO, as well as sputum eosinophil counts assessed at baseline of the SIC were determined. Results A concentration of histamine inducing a 20% decline in FEV1 (PC20) ≤16 mg/mL showed a sensitivity of 87% and a specificity of 36%. A FeNO level ≥25 ppb and a sputum eosinophil count ≥2% provided lower sensitivity rates (47% and 39%, respectively) than the PC20 value. Eight of the 17 subjects without baseline NSBH despite a positive SIC showed a sputum eosinophil count ≥2%, a FeNO level ≥25 ppb, or both outcomes. Combining either a PC20 value ≤16 mg/mL or a FeNO ≥25 ppb increased the sensitivity to 91%. Using either a PC20 ≤16 mg/mL or a sputum eosinophil count ≥1% increased the sensitivity to 94%. Conclusion Adding the assessment of FeNO level and sputum eosinophils to NSBH improves the identification of subjects who may have OA and require further objective testing before excluding the possibility of OA.