Associations between pollen and allergic rhinitis in children and adolescents

Allergic rhinitis (AR) is a type of rhinitis accompanied by sensitization to allergens. One of the most clinically important allergens is pollen. Recently, due to climate change and CO 2 air pollution, the flowering period starts earlier and persists longer. In addition, antigenicity due to environmental pollution is also being strengthened. As a result, the sensitization rate to pollen antigens is on the rise. It is known that the prevalence of AR especially caused by pollen is rapidly escalating. Although the causal relationship between pollen exposure and the severity of rhinitis is not precisely established, an association of rhinitis symptoms with the time of pollen scattering exists. In addition, the mixed effect of environmental pollution and pollen may play a role in the development of rhinitis symptoms. Therefore, in order to avoid pollen, it is necessary to constantly improve pollen forecast and minimize the contact with pollen indoors and outdoors. Treatment of AR should be performed according to guidelines. Also, continuous efforts to solve the environmental problems affecting the ecology of pollen are needed.

Effects of outdoor air pollution on children with allergic rhinitis

The global worsening of air pollution has decreased the quality of life. Air pollutants can induce oxidative stress, epigenetic changes, and alterations to microRNA expression in the airway and skin, leading to immune dysregulation. Previous epidemiological studies suggest a strong association between outdoor environmental pollution and childhood allergic disease, especially allergic rhinitis (AR). Moreover, traffic-related air pollution has increased the severity and incidence of AR, and heavy traffic has been associated with an increased prevalence of AR. Thus, this review aimed to define outdoor environmental pollution and clarify the mechanisms by which air pollutants aggravate AR. In addition, we performed a systematic review and meta-analysis to summarize the findings of several domestic and international epidemiological and clinical studies about the effects of air pollution on AR in children.

The risk of preschool asthma at 2–4 years is not associated with leukocyte telomere length at birth or at 1 year of age

BACKGROUND: Exposure to prenatal stress is associated with offspring allergic-disease development, and oxidative stress may mediate this relationship. OBJECTIVE: We aimed to evaluate whether leukocyte telomere length (LTL) shortening, a marker for exposure to oxidative stress, in early life is associated with increased risk of asthma development during the preschool period. METHODS: We assessed the follow-up clinical data of a subgroup from a birth cohort whose LTLs had been measured from cord-blood and 1-year peripheral-blood samples. We examined whether the LTLs would be associated with asthma development at the age of 2–4 years. RESULTS: The data of 84 subjects were analyzed. LTLs were measured from the cord-blood and 1-year peripheral blood of 75 and 79 subjects, respectively. Among them, 14 subjects (16.7%) developed bronchial asthma between 2–4 years old. Prenatally stressed subjects had marginally increased odds of developing asthma (p = 0.097). There was no significant difference in the odds of preschool-asthma development between the groups with shorter and longer cord-blood LTLs (odds ratio [OR], 0.651; 95% confidence interval [CI], 0.184–2.306) or in the odds between the groups with shorter and longer 1-year peripheral-blood LTLs (OR, 0.448; 95% CI, 0.135–1.483). Finally, subjects with both higher prenatal stress and shorter LTLs did not have significantly higher odds of preschool-asthma development (for cord-blood: OR, 1.242; 95% CI, 0.353–4.368; for 1-year peripheral-blood: OR, 1.451; 95% CI, 0.428–4.919). CONCLUSION: There was no significant association between early life LTLs and higher risk of bronchial-asthma development during the preschool years.

Association of Sensitization to Different Aeroallergens With Airway Function and Nasal Patency in Urban Children

PURPOSE: Children with sensitization to aeroallergens have decreased lung function and nasal patency. Our purpose was to determine the association of sensitization to different aeroallergens with airway function and nasal patency. METHODS: Four hundred and eighty-six randomly selected 11 year-old children who lived in Seongnam City were examined. Serum specific immunoglobulin E (IgE) levels against 6 common allergens (Dermatophagoidesfarinae, birch, cat, dog, Japanese hop and Alternaria), impulse oscillometry (IOS) results for the evaluation of airway dysfunction, and acoustic rhinometry for the determination of nasal airway patency were obtained. RESULTS: IOS indicated that children sensitized to Alternaria (n = 38, 7.8%) and dog dander (n = 69, 14.2%) had decreased lung function, based on resistance at 10 Hz (Rrs10; aβ = 0.0072; 95% CI, 0.017, 0.127; P = 0.010) and 1 Hz (Rrs1; aβ = 0.038; 95% CI, 0.001, 0.074; P = 0.042). Children sensitized to D. farinae (n = 281, 57.8%) had decreased post-decongestant nasal volume at 0 to 5 cm (aβ = −0.605; 95% CI, −1.005, −0.205; P = 0.003), but normal IOS results at all measured frequencies (P > 0.05). Increased serum eosinophil level was associated with Rrs1 (P = 0.007) and Rrs2 (P = 0.018) and post-decongestant nasal volume at 0 to 5 cm (aβ = −0.885; 95% CI, −1.331, −0.439; P < 0.001). CONCLUSIONS: Sensitivity to specific aeroallergens, serum eosinophil count and total IgE level had different associations with upper and lower airway dysfunction in urban children.

Leukocyte Telomere Length Reflects Prenatal Stress Exposure, But Does Not Predict Atopic Dermatitis Development at 1 Year

PURPOSE: Prenatal maternal stress affects offspring's atopic dermatitis (AD) development, which is thought to be mediated by the oxidative stress. We aimed to evaluate the difference in leukocyte telomere length (LTL), a marker for exposure to oxidative stress, according to the prenatal stress exposure and the later AD development. METHODS: From a birth cohort (the COhort for Childhood Origin of Asthma and allergic diseases) that had displayed a good epidemiologic association between the exposure to prenatal stress and AD development in the offspring, we selected 68 pairs of samples from 4 subject groups based on the level of prenatal maternal stress and later AD development. The LTL was measured from both cord blood and 1-year peripheral blood, and their LTLs were compared between subject groups. Finally, the proportion of AD development was examined in the subject groups that are reclassified based on subjects' exposure to prenatal stress and there LTL. RESULTS: Cord-blood LTL was shorter in prenatally stressed infants than in unstressed ones (P = 0.026), which difference was still significant when subjects became 1 year old (P = 0.008). LTL of cord blood, as well as one of the 1-year peripheral blood, was not different according to later AD development at 1 year (P = 0.915 and 0.174, respectively). Shorter LTL made no increase in the proportion of later AD development in either prenatally high-stressed or low-stressed groups (P = 1.000 and 0.473, respectively). CONCLUSIONS: Cord-blood LTL may reflect subjects' exposure to maternal prenatal stress. However, the LTL shortening is not a risk factor of increasing AD development until the age of 1, and a longer investigation may be necessary for validation. Currently, the results doubt the role of LTL shortening as a marker for risk assessment tool for the prenatal stress associated with AD development in the offspring.

Clinical usefulness of serum procalcitonin to distinguish between viral pneumonia and Mycoplasma pneumonia in children: A multicenter, cross-sectional study

PURPOSE: The aim of this study was to compare the clinical usefulness of serum procalcitonin (PCT) levels in Mycoplasma pneumoniae pneumonia (M. pneumonia) and viral pneumonia in children. METHODS: We retrospectively analyzed the medical records of 348 patients admitted between June 2015 and December of 2015. There were 162 patients with M. pneumonia without virus coinfection (group 1) and 186 patients with viral pneumonia (group 2). All subjects had radiographic evidence of pneumonia with available specimens for both M. pneumonia and viral testing, and levels of serum PCT, white blood cell counts (WBC), neutrophil portion, and C-reactive protein (CRP). Fifty-eight children who performed follow-up sampling at the time of no fever for more than 48 hours were subdivided into group 3 (M. pneumonia with follow-up sampling, n=41) and group 4 (viral pneumonia with follow-up sampling, n=17). RESULTS: No difference was noted in the levels of serum PCT (P=0.168), CRP (P=0.296), WBC (P=0.732), and neutrophil proportion (P=0.069) between groups 1 and 2, after adjusting for age. Serial changes in serum PCT levels between the first and second samples were significant in group 3 (P=0.046). Serial changes in serum CRP levels between the first and second samples were significant in group 4 (P=0.008). CONCLUSION: Serum PCT and CRP levels may change differently after infection according to the etiology of pneumonia.

Clinical features of Mycoplasma pneumonia in comparison with viral pneumoina in children: A multicenter, cross-sectional study

PURPOSE: This study was conducted to compare clinical features between Mycoplasma pneumonia and viral pneumonia. METHODS: We retrospectively analyzed the medical records of 428 patients requiring hospitalization among children younger than 18 years of age in 5 hospitals in Seoul and Gyeonggi-do. There were 131 patients with M. pneumonia and virus coinfection, 167 patients with M. pneumonia without virus coinfection, and 130 patients with viral pneumonia. All subjects had radiographic evidence of pneumonia with specimens available for both M. pneumonia and viral testing. Virus was identified using the polymerase chain reaction assay in a nasopharyngeal or oropharyngeal swab. M. pneumoniae pneumonia was diagnosed serologically. RESULTS: Human rhinovirus was detected in 60.3% (79 of 131) of children with M. pneumonia accompanied by virus coinfection. Respiratory syncytial virus (RSV) was detected in 38.2% (50 of 130) of children with viral pneumonia. The mean age was significantly lower in the viral pneumonia group than in the M. pneumonia group with and without virus coinfection. The sex distribution did not differ significantly among the 3 study groups. The procalcitonin level was higher in viral pneumonia and erythrocyte sedimentation rate level was higher in the M. pneumonia group although no significant difference was found in C-reactive protein level between the M. pneumonia and viral pneumonia groups. CONCLUSION: Clinical features and inflammatory markers between M. pneumonia and viral pneumonia may be useful for the treatment of community-acquired pneumonia.

Asthma has an adverse effect on the production of antibody to vaccines

Asthma is considered a chronic inflammatory airway disease. Mounting evidence reports that patients with asthma are at significantly higher risk of developing communicable diseases such as invasive pneumococcal disease, Haemophilus influenza, varicella, measles, pertussis and tetanus. While impaired innate immunity may play a role in increased risk of developing these infections, suboptimal adaptive immune responses have also been reported to play a role in asthmatic subjects with regard to increased risk of infections. This review discusses the currently underrecognized immunological effect of asthma on antibody to vaccines and recommends that clinicians be aware of less optimal antibody production in response to vaccines in subjects with asthma.

Serum Periostin Is Negatively Correlated With Exposure to Formaldehyde and Volatile Organic Compounds in Children

Epidemiological studies have shown that exposure to tobacco smoke causing irritation and inflammation in the airways tends to reduce serum periostin concentrations in adults. We now investigate prospective cross-sectional study on 135 Korean students aged 7 years in the first grade who were participating in the Seongnam Atopy Project for Children's Happiness 2016 (SAP2016) cohort. To the best of our knowledge, this is the first study to show significant inverse correlations between serum periostin concentration and exposure to xylene and formaldehyde in children. Our findings suggested the need for caution in using the serum periostin level as a marker for allergic diseases, since exposure to volatile organic compounds and formaldehyde may confound the interpretation of these results.

Erratum: Seasonal Cycle and Relationship of Seasonal Rhino- and Influenza Virus Epidemics With Episodes of Asthma Exacerbation in Different Age Groups

This erratum is being published to correct the printing error on page 517 of the article. Corrections for Fig. 1 and main text in page 519 are needed. The authors apologize for any inconvenience that this may have caused.

Clinical characteristics and genetic variation in respiratory syncytial virus isolated from infants hospitalized due to acute bronchiolitis in Korea during winter season 2016–2017

PURPOSE: Circulating patterns of predominant respiratory syncytial virus (RSV) genotypes in the community may be helpful in understanding molecular epidemiology and predicting future outbreaks of the RSV genotype. We investigated the association of genetic variations in RSV with acute severe bronchiolitis in infants. METHODS: We reviewed medical records of infants younger than 1 year of age hospitalized due to acute bronchiolitis between November 2016 and February 2017. Subjects were classified as severe or mild based on the use of mechanical or noninvasive ventilation. The associations between severity of the disease, sex, age at admission, oxygen saturation at admission and laboratory test results were analyzed. RSV sequence analysis was performed in the severe group. RESULTS: Among 114 infants, 80 underwent respiratory viral polymerase chain reaction using nasopharyngeal swab; of these, 53 (66.3%) showed positive for RSV. Of the 53 RSV-positive samples, 9 were categorized as the severe group and 44 were categorized as the mild group. Male sex, young age, longer duration of admission, minimum SaO2 at admission and bronchiolitis severity score were significantly correlated with disease severity in the severe group than in the mild group (all variables, P < 0.001). Phylogenetic and sequence analysis in the severe group revealed 8 RSV-A, ON1 genotype and 1 RSV-B, BA4 genotype. CONCLUSION: Phylogenetic types of RSV in subjects of the severe group were RSV-A, ON1 genotype or RSV-B, BA4 genotype which were prevalent in the Korean community at the same time. Our study showed that disease severity was not significantly associated with RSV genotypic evolution or antigenic drift in Korea during winter season 2016–17.

Comorbidities and Phenotypes of Rhinitis in Korean Children and Adolescents: A Cross-sectional, Multicenter Study

PURPOSE: Rhinitis is a nasal inflammatory disease in children and adolescents. However, little is known about the phenotypes and characteristics of allergic rhinitis (AR) in Korean children and adolescents. The objective of this study was to analyze the symptoms and comorbidities of rhinitis, to compare AR to non-allergic rhinitis (NAR), and to reveal the phenotypes and features of AR in a Korean pediatric population. METHODS: Patients under 18 years of age with rhinitis symptoms were recruited from January 2013 to January 2015 by pediatric allergists. We analyzed symptoms, phenotypes, comorbidities, and allergen sensitization in this cross-sectional, multicenter study. RESULTS: Medical records were collected from 11 hospitals. The AR group has 641 (68.3%) patients, with 63.2% of boys and 7.5 (±3.4) years of mean age. The NAR group has 136 (14.5%) patients, with 55.1% of boys and 5.5 (±2.9) years of mean age. Moderate-severe persistent AR affected 41.2% of AR patients. Nasal obstruction was more common in NAR patients (P<0.050), whereas AR patients sneezed more (P<0.050) and more commonly had conjunctivitis, asthma, and otitis media (P<0.050). Sinusitis was the most common comorbidity in both groups. Allergen sensitization was caused by house dust mites (HDMs) (90.2%), pollen (38.7%), and animal dander (24.8%) in AR patients. Pollen and animal dander sensitization significantly increased age-dependently (P<0.050), but 91.9% of AR patients were already sensitized to HDMs before 5 years old. CONCLUSIONS: Our study revealed that AR was more prevalent than NAR and that 41.2% of AR presented with moderate-severe disease in Korean pediatric populations. Sinusitis was the most common comorbidity, and sleep disturbance was associated with the severity of rhinitis. The majority of AR patients were sensitized to HDMs in preschool ages. Further studies, including nationwide and longitudinal data, will help understand the relationship between these diseases.

Treatment of Auricular Deformities with the EarWell System in Three Newborns

Auricular deformities occur frequently in newborn infants. Typically, most pediatricians explain to parents that these deformities will get better as child grows older. But, only about 30% of auricular deformities are known to be self-correcting, and there is no reliable model to predict them. If ear molding is initiated during the first days of life with the EarWell System, successful treatment could be possible without pain in a non-surgical way. We present 3 cases of auricular deformities treated with the EarWell System. 2 infants were born with auricular deformities at Gangnam Cha Medical Center and 1 infant visited the outpatient clinic for the treatment of auricular deformities. 5 ears in 3 infants underwent ear molding using the EarWell System. They had it placed on the 20th day after birth. Average treatment time was 18.7 days, and all of them were corrected. Complications were redness, oozing, erosion and mild pressure ulcerations. Early recognition and treatment of the auricular deformity ensure the great prospect of success. Also, it is important for both the parents and the pediatricians to know that auricular deformities could be successfully treated with Earwell System.

Prevalence of respiratory virus infection with regard to age, sex, and seasonality factors: A single center experience against children hospitalized during the 10 years

PURPOSE: It is well known that respiratory viral infection has epidemiological characteristics, including season. This study aimed to investigate the patterns of the prevalence of common respiratory viruses during a period of 10 years with regard to age, sex, and season in Korean children. METHODS: From June 2006 to November 2016, we obtained 11,798 specimens from patients aged less than 18 years who were admitted with lower respiratory infections. Ten respiratory viruses were detected using multiplex reverse transcription-polymerase chain reaction. RESULTS: Of 11,798 specimens, at least 1 virus was detected in 4,845 (41.1%). Respiratory syncytial virus (RSV, 18.9%) was the most common virus detected, followed by human rhinovirus (HRV, 14.8%), adenovirus (9.5%), and human bocavirus (HBoV, 7.4%). The detection rate of HRV was higher in male subjects (male 60.0% vs. female 40.0%, P=0.004), but the other viruses had no significant differences with regard to sex. The subjects who were positive for RSV test were youngest (median, 10.5 months; interquartile range, 3.0–25.0 months), followed by human coronavirus (median, 13.0 months), HRV (median, 14 months), and parainfluenza (median, 14 months). HBoV was most commonly detected in spring (29.3%), enterovirus in summer (25.8%), HRV in fall (22.6%), and RSV in October and winter (22.6%). CONCLUSION: We found that the prevalence of respiratory viruses in Korean children during a period of 10 years was associated with age, sex, and season when the infection occurred. Further nationwide data is warranted to infer clinical implication of our results.

Seasonal Cycle and Relationship of Seasonal Rhino- and Influenza Virus Epidemics With Episodes of Asthma Exacerbation in Different Age Groups

PURPOSE: Seasonal variations in asthma exacerbation (AE) are associated with respiratory virus outbreaks and the return of children to school after vacation. This study aims to elucidate the period, phase, and amplitude of seasonal cycles of AE in 5 different age groups with regard to rhino- and influenza virus epidemics in Korea. METHODS: The number of daily emergency department (ED) visits for AE in all age groups of Korea and the nationwide weekly incidence of rhino- and influenza virus, were obtained for 2008-2012. Fourier regression was used to model rhythmicity, and the Cosinor method was used to determine the amplitude and phase of the cycles in each age group. The cross-correlation function (CCF) between AE and the rhino- and influenza virus epidemics was also calculated. RESULTS: There were 157,559 events of AE (0.62 events/1,000 individuals/year) during the study period. There were spring and fall peaks of AE in children and adults, but only 1 winter peak in the elderly. The amplitude of the AE peak in infants was higher in spring than in fall (9.16 vs 3.04, P<0.010), and the fall peak was approximately 1 month later in infants than in school children (October 11 vs November 13, P<0.010). The association between AE and rhinovirus was greatest in school children (rho=0.331), and the association between AE and influenza virus was greatest in those aged ≥60 years (rho=0.682). CONCLUSIONS: The rhythmicity, amplitude, and phase of the annual cycle of AE differed among different age groups. The patterns of AE were related to the annual rhino- and influenza virus epidemics.

Asthma and the Risk of Rheumatoid Arthritis: An Insight into the Heterogeneity and Phenotypes of Asthma / 결핵및호흡기질환

Asthma is traditionally regarded as a chronic airway disease, and recent literature proves its heterogeneity, based on distinctive clusters or phenotypes of asthma. In defining such asthma clusters, the nature of comorbidity among patients with asthma is poorly understood, by assuming no causal relationship between asthma and other comorbid conditions, including both communicable and noncommunicable diseases. However, emerging evidence suggests that the status of asthma significantly affects the increased susceptibility of the patient to both communicable and noncommunicable diseases. Specifically, the impact of asthma on susceptibility to noncommunicable diseases such as chronic systemic inflammatory diseases (e.g., rheumatoid arthritis), may provide an important insight into asthma as a disease with systemic inflammatory features, a conceptual understanding between asthma and asthma-related comorbidity, and the potential implications on the therapeutic and preventive interventions for patients with asthma. This review discusses the currently under-recognized clinical and immunological phenotypes of asthma; specifically, a higher risk of developing a systemic inflammatory disease such as rheumatoid arthritis and their implications, on the conceptual understanding and management of asthma. Our discussion is divided into three parts: literature summary on the relationship between asthma and the risk of rheumatoid arthritis; potential mechanisms underlying the association; and implications on asthma management and research.

Allergen sensitization and clinical characteristics in young children with atopic dermatitis

PURPOSE: Few studies have demonstrated the effects of aeroallergen sensitization on the development of atopic dermatitis (AD) in young children. This study aimed to investigate the sensitization rate of food and aeroallergens in AD patients under 2 years of age and to compare clinical characteristics between IgE- and non-IgE-mediated AD patients. METHODS: Children aged less than 2 years who had visited CHA Bundang Medical Center from 2013 through 2016 were enrolled. Allergen sensitization was measured by specific IgE levels for common allergens. Detailed information was obtained using an atopy questionnaire. RESULTS: A total of 173 patients were examined, 118 (68.2%) were male patients. The prevalence of aeroallergen sensitization under 1 year of age was 4.8% and increased to 19.5% for children aged 2 years (P=0.005). The mean age (13.6±6.3 months vs. 9.0±5.1 months, P=0.003) and the proportion of children born prematurel (15.4% vs. 2.3%, P=0.013) were higher in the aeroallergen-sensitized group than in nonsensitized group. Sensitization to food allergens between children aged less than 1 year and 2 years appeared to be similar (61.1% vs. 57.1%, P=0.651). There were no significant differences in clinical characteristics between food allergen IgE-mediated and non-IgE-mediated AD children. CONCLUSION: Aeroallergen sensitization increased markedly in AD patients aged 2 years which is about 4 times that of the general population. However, there were no significant differences in clinical manifestations between allergen IgE-mediated and non-IgE-mediated AD children in both food and aeroallergens.

Prevalence and Risk Factors of Urticaria With a Focus on Chronic Urticaria in Children

PURPOSE: Limited data is available on the prevalence and risk factors of acute and chronic urticaria in children. Our purpose was to determine the prevalence and identify the risk factors of acute and chronic urticaria in Korean children. METHODS: This population-based study examined 4,076 children (age 4 to 13 years) who were enrolled in the 2015 prospective Seongnam Atopy Project (SAP 2015) in Korea. The parents completed an urticaria questionnaire that included questions regarding the duration, severity, and triggering factors of urticaria. Blood sampling (n=464) was performed to measure vitamin D, total eosinophil count (TEC), and total IgE levels, and skin prick tests (n=503) were done. RESULTS: The prevalences of the life-time, acute, and chronic urticaria were 22.5%, 13.9%, and 1.8% (chronic continuous urticaria, 0.7%; and chronic recurrent urticaria, 1.1%), respectively. Acute urticaria was significantly associated with allergic diseases and parental history of allergy (P<0.001), but chronic urticaria was not associated with these clinical factors. There was no significant difference in the 25-hydroxyvitamin D level between subjects with chronic urticaria and controls (P=0.124). Chronic continuous urticaria was associated with living in a new residence (aOR=2.38, 95% CI=1.02-5.54, P=0.044) and belonging to a family with a high income (aOR=4.24, 95% CI=1.24-14.56, P=0.022). CONCLUSIONS: A total of 1.8% of children were found to have chronic urticaria. Living in a new residence and belonging to a family with a high income increased the risk of chronic continuous urticaria.

Clinical predictors of chest radiographic abnormalities in young children hospitalized with bronchiolitis: a single center study / 소아과

PURPOSE: Chest radiography is often performed on patients hospitalized with typical clinical manifestations of bronchiolitis. We aimed to determine the proportion of subjects with pathologic chest radiographic findings and the clinical predictors associated with pathologic chest radiographic findings in young children admitted with the typical presentation of bronchiolitis. METHODS: We obtained the following data at admission: sex, age, neonatal history, past history of hospitalization for respiratory illnesses, heart rate, respiratory rate, the presence of fever, total duration of fever, oxygen saturation, laboratory parameters (i.e., complete blood cell count, high-sensitivity C-reactive protein [hs-CRP], etc.), and chest radiography. RESULTS: The study comprised 279 young children. Of these, 26 had a chest radiograph revealing opacity (n=24) or atelectasis (n=2). Multivariate logistic regression analysis showed that after adjustment for confounding factors, the clinical predictors associated with pathologic chest radiographic findings in young children admitted with bronchiolitis were elevated hs-CRP level (>0.3 mg/dL) and past history of hospitalization for respiratory illnesses (all P<0.05). CONCLUSION: The current study suggests that chest radiographs in young children with typical clinical manifestations of bronchiolitis have limited value. Nonetheless, young children with clinical factors such as high hs-CRP levels at admission or past history of hospitalization for respiratory illnesses may be more likely to have pathologic chest radiographic findings.

Does the different amount of short-acting bronchodilator drugs have different effects on small airway response in bronchodilator test?

PURPOSE: It is recommended to use 200 (2 puffs) or 400 (4 puffs) µg of salbutamol in the bronchodilator response (BDR) test. We aimed to compare the difference between these 2 doses with regard to small airway dysfunction. METHODS: One hundred sixteen subjects who visited the hospital for diagnosis or follow-up of asthma were consecutively enrolled between June 1 and November 31, 2013. The subjects were randomly assigned to the BDR test at the 2 doses (200 or 400 µg of salbutamol), with physicians blinded to the group each subject was assigned to and undertook the BDR test using the spirometry and impulse oscillometry system (IOS). RESULTS: A total of 116 subjects participated in this study; the mean age was 7.8±3.6 years. The number of participants who were assigned to 2 and 4 puffs groups was 59 and 57, respectively. The mean age was older in the 4 puffs group than in the 2 puffs group (P=0.008). There were no significant difference in spirometric and oscillometric parameters between the 2 and 4 puffs groups. However, in subgroup analysis of asthmatic patients on maintenance therapy (n=21), there was a significant difference in relative changes in Rrs5 between the 2 and 4 puffs groups (16.4%±9.6% vs. 28.7%±8.8%, P=0.035). The forced expiratory volume of 1 second showed a significant correlation with resistance in the 2 puffs group and with reactance in the 4 puffs group. CONCLUSION: There was a significant relationship between the amounts of bronchodilators administered and the small airway dysfunction in children with asthma on maintenance therapy. Further research is warranted to delineate changes in spirometric and IOS measures in accordance with the different amounts of bronchodilators administered.