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Relationship between response to inhaled salbutamol and methacholine bronchial provocation in children with suspected
H Bibi1, M Montgomery, H Pasterkamp
1Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
Insights
A 6% increase in FEV1 after salbutamol indicates bronchial hyperreactivity in children with normal baseline lung function. This finding aids in diagnosing asthma in pediatric patients.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Clinical Diagnostics
Background:
- Asthma diagnosis in children often relies on lung function tests.
- Baseline spirometry may appear normal in some children with suspected asthma.
- Bronchial hyperreactivity (BH) is a key feature of asthma.
Purpose of the Study:
- To evaluate the utility of post-salbutamol FEV1 change in identifying BH in children.
- To correlate methacholine challenge test results with bronchodilator response.
Main Methods:
- Fifty children (ages 6-15) with suspected asthma underwent spirometry (FEV1, FEF25-75, FEF50) before and after salbutamol.
- Methacholine challenge testing (PC20) was performed on a separate day to assess bronchial hyperreactivity.
- Fourteen healthy children served as controls.
Main Results:
- A negative correlation was observed between baseline FEV1 and the percent change in FEV1 post-salbutamol.
- 58.3% of patients with PC20 ≤ 0.25 mg/mL showed >6% FEV1 increase; this decreased with higher PC20 values.
- A >6% FEV1 increase after salbutamol identified subjects with PC20 < 8 mg/mL, indicating BH.
Conclusions:
- In children with normal baseline FEV1, a >6% increase post-salbutamol is indicative of bronchial hyperreactivity.
- Salbutamol challenge testing can help detect BH in pediatric asthma evaluations.
- While sensitive, the predictive value of this test for BH requires further consideration.
Abstract:
Fifty children (27 females, 23 males) ages 6-15 years who were referred for evaluation of suspected asthma had baseline FEV1 and FEF25-75 of greater than or equal to 80% and FEF50 greater than or equal to 70% of predicted values. All had these tests repeated on the same day, after inhaling salbutamol. On a subsequent day PC-20 (methacholine) was determined as an index of bronchial hyperreactivity (BH). Fourteen age-matched healthy children (6 females, 8 males) were studied in a similar manner. There was no significant relationship between the PC20 and the change in FEF25-75 or FEF50 following salbutamol. There was a negative correlation between the initial FEV1 (% predicted) and the percent change in FEV1 following salbutamol (P less than 0.01). An increase in FEV1 of greater than 6% occurred in 7/12 (58.3%) patients with PC20 less than or equal to 0.25 mg/mL (Group I); in 7/24 (29.2%) patients with PC20 = 0.26-2.0 mg/mL (Group II); in only 1/14 (7.1%) patients with PC20 greater than 2.1 mg/mL (Group III) and in none of those asymptomatic (control) children with PC20 greater than 8.0 mg/mL (Group IV). All subjects who had a change in FEV1 greater than 6% after salbutamol had a PC20 less than 8 mg/mL and this test detected the majority of patients with severe BH. However, although the sensitivity of the test was 100%, the predictive value was only 36%. We conclude that in the presence of a normal baseline FEV1 a change of greater than 6% following salbutamol inhalation is indicative of bronchial hyperreactivity.