Determination of Normative Values of Fractional Nitric Oxide in Exhaled Breath (FeNO) in Healthy Indian Population

Abstract

SESSION TITLE: Allergy - Asthma Slide SESSION TYPE: Original Investigation Slide PRESENTED ON: Wednesday, October 26, 2016 at 07:30 AM - 08:30 AM PURPOSE: Fractional nitric oxide in exhaled breath (FENO) is increased in diseases with airway inflammation, especially eosinophilic inflammation. To assess the utility of FENO in disease we need to know its normal value in healthy individuals. American thoracic society (ATS) has given upper limit of normal FENO values as 50 ppb but studies have shown variability in FENO values among different populations. There is no data available about FENO values in healthy Indians. METHODS: Study was conducted at a tertiary care centre in Delhi, India. Four hundred healthy non-smoking adults (age ≥18 years) with normal spirometry were enrolled. The subjects included medical students, hospital staff and patient relatives. Individuals with previous history of respiratory illness, allergic rhinits, atopy and family history of asthma were excluded. All underwent anthropometry and fractional exhaled nitric oxide measurement using hand held NIOX MINO - point of care device (electrochemical sensor based gas analyser). Population was divided into three arbitrary age groups - ≤ 30 years, 31-49 years and ≥50 years. Mann-Whitney U test was done for in-between group comparisons and Spearman’s correlation coefficient was assessed between FENO and various parameters. RESULTS: The mean age of sampled population was 39.6 ± 15.1 years and 263 (65.7%) were males. The median FENO value was 21 ppb (IQR 16-26, range 5-106) with upper and lower limit of normal being 41.5 ppb and 10 ppb respectively. The number of subjects in ≤ 30 years, 30-49 years and > 50 years age groups were 144, 123 and 133 respectively. The median (range, ULN) FENO value in subjects ≤ 30 years, 30-49 years and > 50 years age groups was 20 (6-106, 45) ppb, 22 (5-57, 41) ppb and 22 (7-103, 41) ppb respectively (p = 0.09). FENO values were significantly higher in males [median (IQR) 22 (18-28) ppb] compared to females [median (IQR) 18 (13-23) ppb] (p = 0.001). FENO correlated significantly with height, weight, FEV1 and FVC with correlation coefficients of 0.21 (p<0.001), 0.11 (p=0.02), 0.16 (p<0.001) and 0.18 (p<0.001) respectively. CONCLUSIONS: Upper limit of normal cut-off for FENO in healthy Indians was found to be 41.5 ppb and values above this in an individual will merit further investigation to assess for airway inflammatory states. CLINICAL IMPLICATIONS: Elucidation of normal FENO value in healthy Indian population will help in identifying individuals with airway inflammation among those presenting with respiratory symptoms. DISCLOSURE: The following authors have nothing to disclose: Saurabh Mittal, Anant Mohan, Randeep Guleria, Karan Madan, Vijay Hadda, Gopi Khilnani No Product/Research Disclosure Information