Exhaled nitric oxide and screening for occupational asthma in two at-risk sectors: bakery and hairdressing

BACKGROUND: Fractional exhaled nitric oxide (FENO) levels are increasingly being used in the diagnosis and management of asthma. However, this indicator has rarely been used to detect occupational asthma. OBJECTIVES: To examine non-invasive methods to estimate airway inflammation. METHODS: A nested case-control study was conducted among a retrospective cohort of young workers in the bakery, pastry-making and hairdressing industries. Subjects underwent a clinical examination during a medical visit. Blood samples were collected and FENO levels measured. Cases were subjects diagnosed as suffering from 'confirmed' or 'probable' occupational asthma. RESULTS: Of the 178 workers included in the study, 19 were cases. In univariate analysis, FENO was associated with case/control status, and height and smoking status. In a multiple linear regression model, case/control status (P < 0.001), height (P = 0.006) and smoking status (P < 0.001) remained independent risk factors for variations in FENO levels. Good or fair sensitivity of respectively around 80% and 70% can be achieved using low FENO thresholds (8.5 and 10.5 ppb, respectively). FENO >8.5 ppb and a positive clinical examination increases specificity without loss of sensitivity (to 80.5% and 79.0%, respectively). CONCLUSIONS: This study suggests that FENO measurements alone cannot be considered a useful screening test for occupational asthma. Further investigations are needed to investigate the use of combined FENO and questionnaire or repeated measures.