Ethnic Differences in Fraction of Exhaled Nitric Oxide and Lung Function in Healthy Young Children

Background: Ethnic differences in lung function in school-aged children and adults are well recognized, but little is known about such differences in preschool children. We investigated whether differences exist in fraction of exhaled nitric oxide (FENO), multiple-breath washout (MBW) indices, specific airways resistance (sRaw), and spirometry indices between healthy preschool children of South Asian and white European origin. Methods: FENO, MBW indices (lung clearance index, functional residual capacity, conductive airways inhomogeneity, and acinar airways inhomogeneity), sRaw, and spirometry were measured in healthy South Asian and white children aged 4 to 6 years, and comparisons were made between the two groups. Statistical analyses were by multiple linear regression and t tests. Results: Thirty-seven white (mean age 5.8 +/- 0.7 years, 49% boys) and 31 South Asian children (mean age 5.4 +/- 0.8 years, 52% boys) were recruited. FENO was, on average, 36% higher (P < .05) in South Asian children compared with white children. FVC and FEY, and fractions thereof (FEV0.75 and FEV0.5) z-scores were significantly lower in South Asian compared with white children by 0.69 (P = .01), 0.76 (P = .004), 0.76 (P = .009), and 0.85 (P = .002) z-scores, respectively, but there were no significant differences in FEV1/FVC, FE25-75, sRaw, or MBW indices. Conclusions: Differences in FENO and forced expiratory lung volumes between South Asian and white children exist from a very young age. Ethnic differences should be taken into account when interpreting lung function results in preschool children for effective management of respiratory conditions. CHEST 2011; 140(5):1325-1331