Normal reference values of Fractional Exhaled Nitric Oxide (FENO)in healthy Indian primary school children

Abstract

<b>Background:</b> The measurement of Fractional Exhaled Nitric Oxide(FENO) is non-invasive, quick and easy to do. The current ERS(Gaillard:ERJ:2021)and NICE guidelines(2017) recommend measurement of FENO to support a diagnosis of asthma in children ≥ 5 years with cut off values of &gt;25 and &gt;35 parts per billion(ppb)respectively as significant. We undertook this study as the measurement of FENO is influenced by several factors including ethnicity(Kovesi:Chest:2008)and there is limited data available from India <b>Aims:</b> We aimed to establish normal FENO values in healthy school-aged Indian children. The objective was to assess whether cut-offs proposed by ERS and NICE were applicable to our population <b>Methods:</b> Prospective cross-sectional study conducted at the out-patient division of a tertiary paediatric centre in western India between July-October 2021. Children with asthma, history of wheezing and allergic rhinitis were excluded. FENO was measured by a single breath technique as per the manufacturers’ recommendation <b>Results:</b> 141 children were recruited. There were 63 girls(44.6%) and 78 boys(55.4%). Median age of the population was 8 years(range-5-12 years). Median FENO value was 9 ppb(range- 3.5 -53 ppb). Median FENO in boys was 8 ppb(range- 3.5- 53) and girls was 8 ppb(range- 3.5 - 42), the difference was not statistically significant(p value 0.516). 98.5% of patients had a value of less than 35ppb and 94.3% had a value of less than 25ppb <b>Conclusion:</b> Our study, for the first time provides normal FENO levels in healthy school age children from India. Cut off values recommended by the ERS and NICE asthma guidelines can be applied to school aged children from India for management of asthma.