Pulmonary function testing in the preschool-aged population has gained significant support as several carefully designed and implemented clinical studies have shown children in this age group to be able to successfully perform the test (3
). This is the first study to evaluate the use of spirometry in preschool children in the context of a busy, clinic-based, pulmonary function testing laboratory under normal clinical conditions. Our findings show that on the first occasion of performing spirometry, more than half of preschool-aged children are able to produce acceptable and repeatable spirometry based on the recommendations put forth in the 2007 ATS/ERS statement on the use of pulmonary function testing (PFT) in preschool-aged children. We found that over 80% of children were able to produce at least one acceptable spirometry effort, with 54% able to repeat similar efforts.
The success rate in our study is lower than many prospective studies assessing spirometry in similarly aged children, which have found acceptable and repeatable results in 65% to 92% of subjects (4
). The direct comparison is limited in that the referenced studies had varied criteria for determining acceptability and reproducibility, as there was no international guiding standard. This study adds to the important work done by Loeb et al. (5
) who prospectively studied a cohort of children of all ages in light of the 2007 ATS/ERS criteria. For the 33 4- to 5-year-old children included in that study, they reported a success rate to produce acceptable and repeatable spirometry of roughly 42%. The current study greatly expands the power to determine a success rate in preschool-aged children because it draws from nearly 250 4- to 5-year-old subjects. Our overall success rate of 54% for these children is greater than that found by Loeb and colleagues and may reflect differences in sample size favoring the current study to more closely approximate the true population success rate. However, differences in the study cohorts, spirometry coaching, and subjective interpretations of spirometry by reviewers may have also played a role. Crenesse et al. (18
) found similar success rates (55%) in a cohort of 355 3- to 5-year-old children who were also studied in a retrospectively designed study when using similar criteria for repeatability. In that study repeatability was defined as change less than 0.1 L or 5%, as opposed to 0.1 L or 10% in the current ATS criteria, and the acceptability criteria were directly adapted from adult guidelines (18
). In a prospective clinical trial, the PEAK study also reported a success rate of 56% in young children, though the criteria for acceptability and repeatability were not well described (20
This study offers the unique perspective of spirometry performed in a busy clinic-based PFT laboratory during routine clinical conditions. These conditions differ from those offered in prospective clinical trials, which enjoy the benefit of a carefully recruited population and dedicated research staff, and they likely reflect a more accurate depiction of what a clinician may encounter. Consistent with this notion is that many prospective studies had much higher success rates, which may reflect the special conditions of the research laboratory that do not exist in routine clinical practice. Furthermore, this is the largest study to analyze spirometry in the context of the 2007 ATS/ERS statement on pulmonary function testing in preschool children.
We present the age-specific acceptability and repeatability data () in an effort to fully illustrate the stratification of the results by age group and the effect on the success rate as a whole. Our clinical practice is such that 4-year-old children are generally referred for spirometry after a practitioner has seen the child and deemed him or her to have an adequate level of maturity and cooperation to be successful with the test. On the other hand, most 5-year-old children are routinely referred for pulmonary function testing, especially if they are known or suspected of having a chronic respiratory disease. Even if the practitioner is doubtful any useful information will be gained, spirometry referral is still made in order to introduce the test to the child and to provide some practice. As this is a retrospective study specifically looking at the real-life clinical feasibility of performing spirometry on preschool-aged children, it was impossible to avoid this degree of selection bias. However, the data collected on 5-year-old children likely reflects the true ability of children in this age group, as it is a normal age for beginning spirometry in our practice and the success rates reported here are similar to some prospective studies (10
). We feel that the data for the 4-year-old children is still instructive. Although the success rate for the younger children may be inflated, the sample size of 53 4-year-old children is large enough to show that it is not a rare event to find 4-year-old children who are able to perform spirometry, even if screening for the most cooperative ones. As previous studies have reported, consistent use of computer incentive programs may better elicit informative spirometry (3
). Furthermore, we only looked at efforts for children naïve to performing spirometry in order to consistently compare subjects. We anticipate that the success rate of performing spirometry will be greatly increased after children practice spirometry over several visits, thus the numbers we report here are likely to be a conservative estimate of the clinical utility over time.
In this study, none of the selected variables were significant predictors of successful completion of spirometry. We looked specifically at gender, race, age, and several of the most common diagnoses in this age group. In large part, this corroborates previous findings that gender, race, and primary diagnosis do not predict successful spirometry (3
). It has been suggested that children with neuromuscular disease are less likely to perform successful spirometry (5
); however, we were unable to test this hypothesis because there was only one child in our cohort with neuromuscular disease.
Although the focus of this study was to determine feasibility of preschool-aged children to perform adequate spirometry in the clinical setting, we further attempted to determine the clinical utility of these measurements. When preschool children with asthma and cystic fibrosis were compared with the predicted spirometry values for age and height (4
), most parameters of forced expiratory volume were close to 100% predicted. FVC was found to be lower than predicted, particularly for the asthmatic group; however, the distribution of values was large. It may not be surprising that this group did not have significant differences than the normative values, as children with asthma frequently have normal lung function when well. Although in older children spirometry is important in the diagnosis and management of asthma (2
), it is less clear in the preschool age group (8
). However, it is important to note that 18% of children with asthma had an FEV1
less than 80% predicted and 31% had an FEF25–75%
, an important measure of small- to medium-sized airway disease, less than 80% predicted. When all children able to complete at least two acceptable and repeatable maneuvers were included, there was even greater variability and a larger proportion of children with abnormal lung function was identified. For these children, spirometry may offer important clinical information that may influence the management of the child’s respiratory disease. This type of airflow obstruction has been reported elsewhere for cohorts of children with symptomatic asthma (13
) and cystic fibrosis (15
), corroborating spirometry’s usefulness as a diagnostic tool.
This post hoc analysis is limited by the lack of bronchial hyperresponsiveness or bronchodilator reversibility data for children diagnosed with asthma, which may have led to misclassification in some cases. Although there are some data on the feasibility of bronchoprovocation testing in preschool-aged children (22
), this was not routinely done in our clinical practice during the study period. In this study, we rely on physician diagnosis as indicated by the clinician at the time of ordering the spirometry test.
In conclusion, we demonstrate that a majority of preschool-aged children naïve to spirometry are able to perform acceptable and repeatable spirometry in a busy PFT laboratory under normal clinical circumstances; however, the clinical success rate may be lower than described by previous prospective clinical trials. These findings are an important clinical correlate to the mounting evidence that spirometry is an appropriate test in this age group. Further studies are needed to address the clinical utility of spirometry in the diagnosis and management of chronic respiratory diseases, such as asthma and cystic fibrosis, in preschool-aged children.