PURPOSE: Assay of exhaled Nitric Oxide (eNO) is a relatively new and non-invasive test considered useful in asthma control assessment. The purpose of this pilot study is to compare the accuracy of eNO, FEV1 and FEV1/FVC as objective tools for asthma control assessment. The study was done in an urban, pediatric asthma clinic in Fresno, California.
METHODS: A retrospective chart review of children with persistent asthma 5-18 years of age, on inhaled corticosteroids attending asthma clinic during the past 2 years was done. Asthma control was classified as either ‘well controlled’ or ‘not controlled’. FEV1 and FEV1/FVC were estimated by office spirometry performed by the same trained technician in all cases. Only spirometry curves that met the 2005 ATS acceptability criteria were included. Level of asthma control based on symptom review, corresponding FEV1, FEV1/ FVC and eNO levels on the same visit were obtained. The accuracy of the three continuous test variables was analyzed using a ROC analysis. Area under the curve and confidence interval were calculated using non-parametric methods. The association between serum IgE and eNo was tested using linear regression analysis.
RESULTS: We analyzed 92 data sets from 62 asthmatics,37 males and 25 females. Asthma was documented as ‘well controlled’ in 41 and ‘not controlled’ in 51 visits. Among the three test result variables, both FEV1 and eNO were found to be useful, but eNO appeared to be a better tool for assessing asthma control. FEV1/ FVC ratio was not found to be useful. At the established cut off level of 20ppb of eNO as the upper limit of normal in children, the specificity for predicting asthma control was 82% and sensitivity 55% in this cohort. The area under curve for ROC analysis for eNO was 0.759 (95% CI, 0.66-0.85;p<0.001).There was a significant association between eNO and serum IgE values.
CONCLUSIONS: Estimation of eNO proved to be a better objective tool for assessing asthma control than FEV1 estimation in our cohort from this pilot study. Our results indicate that eNO assay is an alternate, non-invasive objective tool to assess asthma control.
CLINICAL IMPLICATIONS: Estimation of eNO is a useful test in the decision making process in asthma management in children especially when history is unreliable and spirometry is either difficult or unavailable.
DISCLOSURE: The following authors have nothing to disclose: Maries Joseph, Poonam Vijayavargia
No Product/Research Disclosure Information