Effective allergen avoidance reduces residual volume and sputum eosinophils in children with asthma

Letters to the Editor Effective allergen avoidance reduces residual volume and sputum eosinophils in children with asthma To the Editor: We report changes in residual volume (RV) and sputum eosinophils in 15 house dust mite (HDM)–sensitized children with asthma (6-14 years of age) while they resided at our Institute in Misurina, in the Italian Alps. At the Institute, the routine analysis for HDM always failed to demonstrate presence of mite allergens. RV is considered a reliable index of air trapping in chronic asthma, and it might be a useful means of verifying obstruction and inflammation of the small airways.1 Likewise, sputum eosinophils have been suggested as a sensitive index for evaluating the degree of airway inflammation in bronchial asthma.2 The children arrived at high altitude in September 1999 from their hometowns, where they had been living in the presence of allergens. After staying in Misurina for 3 months (until December 20), they went back home for 15 days during the Christmas holidays, during which time they were once again exposed to the offending HDM allergen. Evaluations were performed at 3 time points: in September (T1), within 3 days of the first admission to the Institute; in December (T2), after a 3 months’ stay; and in January (T3), on the return to the Institute after 2 weeks at home. Lung volume measurements were obtained through use of a watersealed lung volume spirometer, which uses a washout system with removal of CO2, an O2 delivery control system, and analysis of the helium dilution by a fast response cell (Baires, Biorevo mod, Biomedin, Padova, Italy). Sputum was induced by inhalation of hypertonic saline solution in accordance with a standardized method.2 Comparisons were performed through use of the Wilcoxon signed-rank test and correlations through use of the Spearman correlation test. Fig 1 shows the changes in RV and sputum eosinophil count. RV (mean ± SEM) decreased significantly after 3 months at high altitude, from 117.6% ± 8.6% of predicted at T1 to 98.0% ± 3.8% at T2 (P < .02), with a following increase at T3 (133.3% ± 20.8%; P < .05). FEV1 and forced expiratory flow at 25% to 75% of forced vital capacity (FEF25-75) improved gradually without reaching statistical significance throughout the period of observation. The respective FEV1 and FEF25-75 values, each expressed as a percent of predicted, were as follows (median, Q1, Q3): 103% (99% to 108%) and 84% (67% to 93%) at T1, 106% (98% to 110%) and 92% (75% to 100%) at T2, and 107% (99% to 115%) and 94% (78% to 113%) at T3. The percentage of sputum eosinophils (Fig 1) decreased significantly between T1 and T2, from 9.0% ± 2.9% to 3.2% ± 0.9% (P < .05). Eosinophil counts increased in January (at T3; 5.9% ± 1.6%) after 2 weeks at home, where there was exposure to HDM (P < .05). No significant correlation was observed between all of the investigated parameters. The mean ± SD exposure to HDM in the children’s homes, expressed as micrograms of mite group I allergens per gram of dust, was 21.2 ± 4.0. In these subjects, 3 months of real HDM avoidance, accompanied by reductions in passive smoke and air pollutant exposure and viral exacerbation, resulted in a significant reduction in the percentage of sputum eosinophils. Our data might confirm that RV is a sensitive index of airway inflammation changes.2 The observed reduction in RV could reflect a reduction of bronchial edema, granulocyte influx, and airway inflammation at the small airway level.3 RV represented a more sensitive lung parameter of airway inflammation than either FEV1 or FEF25-75, which improved only slightly during 308

FIG 1. Residual volume and sputum eosinophil variation at each time point of the study. Results are expressed as means ± standard errors of the estimate. RV, Residual volume; T1, September; T2, December; T3, January.

the observation period and did not differ significantly during the period of allergen avoidance or exposure. In our subjects, RV was significantly increased during the allergen exposure periods. Increased RV has previously been observed to be associated with decreased lung elasticity and with more severe asthma exacerbation.4 Our data thus might support the use of lung volume measurement in children with asthma, even when the disease is apparently well controlled, especially on exposure to relevant allergens. Furthermore, our results suggest the advantage of allergen avoidance measures. Diego G. Peroni, MDa Giorgio L. Piacentini, MDa Lucia Vicentini, BSca Silvia Costella, BScb Angelo Pietrobelli, MDa Attilio L. Boner, MDa aClinica Pediatrica Universita’ di Verona Policlinico GB Rossi, Piazzale Scuro 10 37134 Verona, Italy bIstituto Pio XII, Misurina, Italy REFERENCES 1. Stanescu D. Small airways obstruction syndrome. Chest 1999;116:231. 2. Pizzichini E, Pizzichini M, Efthimiadis A, Dolovich J, Hargreave FE. Measuring airway inflammation in asthma: eosinophils and eosinophilic cationic protein in induced sputum compared with peripheral blood. J Allergy Clin Immunol 1997;99:539-44. 3. Kraft M. The distal airways: are they important in asthma? Eur Respir J 1999;14:1403-17. 4. Liu AH, Brugman SM, Schaeffer EB, Irvin CG. Reduced lung elasticity may characterize children with severe asthma. Am Rev Respir Dis 1990;141:A906.

1/8/117174 doi:10.1067/mai.2001.117174