The Correlation of Fractional Exhaled Nitric Oxide Level With the Absolute Eosinophil Count and Level of Bronchial Asthma Control

Abstract

diagnosed with Bronchial asthma as defined by GINA, were included. The participants were grouped according to the level of asthma control. Spirometry was done for participants who were diagnosed with asthma based on symptoms only. FeNO analysis was performed on the same visit. Eosinophil count were collected and recorded. Correlation between Asthma severity and FeNO levels was determined and tested using Spearman correlation analysis, and graphically presented using box and whiskers. The level of significance was set at 0.05. RESULTS: Our study revealed that older age groups (mean age 60 + 14) had the tendency to develop uncontrolled asthma, and higher FeNO levels, although baseline demographics and clinical characteristics were not statistically significant. The lowest mean FeNO seen among patients with controlled asthma was 25.55 + 4.70 with a significant increase in the concentration of FeNO (53.86 + 25.89) as Asthma becomes uncontrolled, p¼0.001. Higher FeNO levels were strongly correlated with uncontrolled asthma, r¼0.78. A cut off value of >41 ppb had a sensitivity of 71.43% and specificity of 76.47% in predicting uncontrolled Bronchial Asthma On the other hand, the difference in the absolute eosinophil count among the groups was not statistically significant, p¼0.90, but still revealed a weak positive correlation, r¼0.33. A cut off value >0.4 Â109/L was noted to have a sensitivity of 71.43% and specificity of 58.82% in predicting uncontrolled Asthma. CONCLUSIONS: This study was able to ascertain that FeNO levels equal or above 41 ppb is associated with uncontrolled Asthma. Although absolute eosinophil count above or equal to 0.4 Â109/L is sensitive in predicting uncontrolled asthma, this parameter was not specific. Hence, an elevated FeNO measurement is more sensitive in accurately predicting uncontrolled asthma as compared to absolute eosinophil counts. CLINICAL IMPLICATIONS: Fractional exhaled nitric oxide levels may have a role in the monitoring of asthma control and confirm adherence to therapy.