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Variability of peak expiratory flow rate in children: short and long term reproducibility
T Frischer1, R Meinert, R Urbanek
1University Children's Hospital, Vienna, Austria.
Insights
Peak expiratory flow (PEF) variability is not a reliable method for screening asthma in young children due to poor reproducibility. This study highlights limitations in using PEF variability for early asthma detection in pediatric populations.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Epidemiology
Background:
- Peak expiratory flow (PEF) variability is explored as a potential indicator of bronchial hyperresponsiveness.
- Previous studies established normal PEF variability ranges in children and utilized it for asthma screening.
- Limited data exists on the reproducibility of PEF variability measurements in epidemiological studies.
Purpose of the Study:
- To assess the reproducibility of peak expiratory flow (PEF) variability measurements in primary school children over two consecutive years.
- To evaluate the utility of PEF variability as a screening tool for asthma in a pediatric cohort.
Main Methods:
- A cohort of primary school children had PEF variability recorded over one week in the first year and two weeks in the second year.
- Measurements were taken twice daily (morning and evening) using mini Wright peak flow meters.
- Average amplitude as a percentage of mean was calculated to quantify PEF variability; increased variability was defined as exceeding the 90th percentile.
Main Results:
- Only 19.7% of children with increased PEF variability in year one showed abnormal results in year two.
- Children with normal PEF variability in year one had an 8.1% chance of abnormal results in year two (OR 2.8).
- Sensitivity and specificity for doctor-diagnosed asthma were 36.4% and 91.0% respectively, with minimal improvement when using extended measurement periods.
Conclusions:
- The assessment of PEF variability in young children for asthma screening has limited value.
- Low reproducibility of the PEF variability method hinders its effectiveness in epidemiological settings for asthma detection.
Background:
Variability of peak expiratory flow (PEF) has been proposed as a surrogate for bronchial hyperresponsiveness. The normal range of variability of PEF for children has been reported and the test has been used to screen for asthma in population based studies. However, there is little information on the reproducibility of the method in epidemiological settings.
Methods:
In a cohort study of primary school children the variability in PEF was recorded in two consecutive years for one week (first survey) and two weeks (second survey) using mini Wright peak flow meters. PEF was recorded twice daily (morning and evening) and average amplitude as a percentage of mean was calculated as a standard measure of PEF variability for each single week of PEF measurement. Children with PEF variability exceeding the 90% percentile of the distribution for the specific time period were regarded as having increased variability of PEF.
Results:
Of 66 children with increased PEF variability in the first year, 13 (19.7%) had an abnormal test in the first week of the second year. Of 543 children with normal PEF variability in the first year, 44 (8.1%) had an abnormal test in the second study year (odds ratio 2.8, confidence interval (CI) 1.4 to 5.4). Of 646 children in the second survey 61 (9.4%) were abnormal during the first week and 68 (10.5%) had an increased PEF variability during the second week, but only 24 (3.7%) children had an increased PEF variability in both weeks. The sensitivity (specificity) for doctor-diagnosed asthma (12 month period prevalence) was 36.4% (91.0%) in the first week of the second survey. When measurements of both weeks of the second survey were used to calculate PEF variability there was little improvement in the sensitivity (38.1%) and specificity (91.5%), mainly because of decreased compliance in the second measurement week.
Conclusions:
In young children assessment of PEF variability in order to screen for asthma is of limited value because of the low reproducibility of the method.