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Comparison of two methacholine challenge methods using Spira-2 or Mefar dosimeter
R Jõgi1, C Janson, H Hedenström
1Lung Clinic, Tartu University, Estonia.
Clinical Physiology (Oxford, England)
|August 19, 1999
Summary
Comparing two bronchial challenge dosimeters, Spira and Mefar, in asthma patients revealed significant differences in methacholine provocative dose 20 (PD20) and FEV1 decline. These findings highlight the need for validated transition equations when comparing bronchial reactivity data obtained with different methods.
Area of Science:
- Pulmonology
- Pharmacology
- Medical Devices
Background:
- Bronchial challenge testing is crucial for diagnosing and managing asthma.
- Breath-actuated dosimeters are commonly used, but variations in protocols may affect results.
- Standardization of methacholine challenge protocols is essential for accurate assessment of bronchial hyperresponsiveness.
Purpose of the Study:
- To compare the performance of two breath-actuated dosimeters, Spira Elektro-2 and Mefar, in bronchial challenge testing.
- To evaluate differences in methacholine provocative dose 20 (PD20) and dose-response curves between the two protocols.
- To establish transition equations for comparing data obtained from the Spira and Mefar dosimeters.
Main Methods:
- A comparative study involving 28 patients with mild to moderate asthma.
- Methacholine bronchial challenges were conducted using Spira Elektro-2 and Mefar dosimeters in a randomized order.
- Provocative dose 20 (PD20) and the slope of the forced expiratory volume in 1 second (FEV1) decline on log(dose) were calculated and compared.
Main Results:
- The provocative dose 20 (PD20) for methacholine was significantly lower with the Spira dosimeter compared to the Mefar dosimeter.
- The decline in FEV1 relative to the log of the methacholine dose was steeper with the Spira protocol.
- Linear regression analysis yielded transition equations for converting PD20 and slope values between the two dosimeters, with significant correlation coefficients (r=0.62 for PD20, r=0.51 for slope).
Conclusions:
- The Spira Elektro-2 dosimeter protocol resulted in a lower PD20 and a steeper FEV1 decline compared to the Mefar protocol.
- Differences in dosimeter methods necessitate the validation and calculation of transition equations for accurate comparison of bronchial reactivity data.
- These findings underscore the importance of considering the specific dosimeter and protocol used when interpreting results from methacholine challenges.
