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

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.

To examine non-invasive methods to estimate airway inflammation.

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.

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).

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.