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Sample size estimation in studies monitoring exercise-induced bronchoconstriction in asthmatic children
W B Hofstra1, J K Sont, P J Sterk
1Department of Pulmonary Pediatrics, Juliana Children's Hospital, The Hague, The Netherlands.
Insights
Standardized treadmill exercise tests are repeatable for assessing exercise-induced bronchoconstriction (EIB) in children with asthma. This method is reliable for research and clinical use, requiring fewer participants than previously thought.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Clinical Exercise Physiology
Background:
- Exercise-induced bronchoconstriction (EIB) is common in asthmatic children.
- The repeatability of standardized treadmill exercise testing for EIB in children was not well-established.
- Previous research lacked robust data on test-retest reliability for EIB assessment in pediatric populations.
Purpose of the Study:
- To evaluate the repeatability of standardized treadmill exercise testing in asthmatic children with EIB.
- To determine the reliability of using dry air and heart rate monitoring during exercise tests.
- To establish sample size estimations for future EIB studies in children.
Main Methods:
- Twenty-seven asthmatic children with known EIB underwent two standardized treadmill tests within three weeks.
- Tests involved breathing dry air, aiming for 90% of predicted maximum heart rate.
- Response was measured by the percentage fall in forced expiratory volume in one second (FEV1) and area under the curve (AUC).
Main Results:
- Intra-class correlation coefficients for % fall and AUC were 0.57 and 0.67, respectively.
- Power curves indicated that only 12 patients might be sufficient to detect a 50% drug-induced reduction in EIB.
- These findings suggest adequate repeatability for research and clinical applications.
Conclusions:
- Standardized treadmill exercise testing using dry air and heart rate monitoring demonstrates adequate repeatability in children with asthma and EIB.
- The findings support the use of this testing protocol in both research settings and clinical practice.
- This methodology can inform efficient study designs for evaluating EIB interventions in pediatric populations.
Background:
The repeatability of the response to standardised treadmill exercise testing using dry air and monitoring of heart rate in asthmatic children suffering from exercise-induced bronchoconstriction (EIB) has not been well established.
Methods:
Twenty seven asthmatic children with known EIB performed standardised exercise testing twice within a period of three weeks. The tests were performed on a treadmill while breathing dry air. During both tests heart rate had to reach 90% of the predicted maximum. Response to exercise was expressed as % fall in forced expiratory volume in one second (FEV1) from baseline and as area under the curve (AUC) of the time-response curve.
Results:
The intra-class correlation coefficients for % fall and AUC (log-transformed) were 0.57 and 0.67, respectively. From these data, power curves were constructed that allowed estimations to be made of sample sizes required for studies of EIB in children. These indicated that, if a drug is expected to reduce EIB by 50%, as few as 12 patients would be sufficient to demonstrate this effect (90% power) using a parallel design study.
Conclusions:
Standardised exercise testing for EIB using dry air and monitoring of heart rate is adequately repeatable for use in research and clinical practice in children with asthma.