It was shown that fractionated exhaled nitric oxide (FENO) is suppressed by tobacco smoking. This might prevent its use in asthma follow-up of smoking patients while FENO appears to be a reliable marker of asthma control in non smoking asthma patients. In this study, we compared the ability of FENO to reflect changes in asthma control as assessed by the Asthma Control Questionnaire (ACQ) in smoking and non smoking asthmatics.
Methods
FENO and ACQ were recorded at least twice in 155 non smoking and 36 smoking patients suffering from asthma and treated with similar ICS doses (≤500μg eq. BDP day-1). FENO ability to reflect improvement (ΔACQ < -0.5), optimisation (ACQ < 0.75) or deterioration (ΔACQ > 0.5) in asthma control was evaluated using the ROC curve technique.
Results
FENO levels were lower in smoking asthma patients (28 ppb vs 48 ppb; p < 0.001) despite similar ACQ scores (1,7). FENO decreases <40% and <20% preclude asthma control optimisation in non smoking and smoking patients respectively (VPN = 79% and 89%). FENO decreases <20% and <10% preclude asthma control improvement in those groups of patients (VPN = 78% and 72%). FENO increase <10% excludes a significant deterioration in asthma control in both populations (VPN = 85% and 89%).
Conclusions
Although FENO levels are reduced in smoking- as compared to non smoking- asthma patients, FENO is nearly as reliable as a marker of change in asthma control in both populations. However, different cut-off values must be considered when evaluating improvement and optimisation of asthma control in smoking and non smoking asthma patients.
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