Chest
Volume 136, Issue 1, July 2009, Pages 184-189
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Original Research
Lung Function Testing
Application of a Shortened Inhaled Adenosine-5′-Monophosphate Challenge in Young Children Using the Forced Oscillation Technique

https://doi.org/10.1378/chest.08-2848Get rights and content

Background

Adenosine-5′-monophosphate (AMP) is an indirect challenge agent thought to reflect allergic airway inflammation. The forced oscillation technique (FOT) is ideal for use in young children and is suitable for inhaled challenge studies in patients who are in this age group. We assessed the agreement between a shortened and a standard AMP challenge and the repeatability of the shortened AMP challenge using FOT as a primary outcome variable.

Methods

Eighteen children completed a shortened and a standard AMP challenge, and 20 children completed repeated shortened AMP challenges. The children inhaled nebulized AMP tidally for 2 min, following which the presence of wheeze and pulse oximetric saturation (Spo2) was recorded prior to FOT measurement. Testing continued until the maximum dose was reached or until wheeze, a decrease in Spo2 to < 90%, or an increase in respiratory resistance at 8 Hz of 2.0 hPa/s/L or 30% was noted. Concordance was assessed as a binary response, and agreement in provocation concentrations (PCs) causing a response was assessed with intraclass correlations.

Results

There was a high degree of concordance between the shortened and standard AMP protocols (94%) and repeated shortened AMP protocols (100%). The mean log10 PCs displayed a high degree of agreement for both AMP protocols, with intraclass correlation coefficients of 0.94 (95% confidence interval, 0.85 to 0.98) and 0.94 (95% confidence interval, 0.82 to 0.98), respectively.

Conclusions

We demonstrated that a shortened AMP challenge that can be applied to young children is comparable to the standard AMP challenge and is highly repeatable. Further studies in young children to assess the clinical role of a shortened AMP challenge using FOT are required.

Section snippets

Subjects

Forty-one children (25 boys; age range, 3.5 to 7.5 years) underwent paired inhaled AMP challenges. Nine children had a history of respiratory symptoms (parent-reported wheeze, asthma, or persistent cough without colds, but not in the past 12 months), 30 children had current wheeze (parent-reported wheeze, asthma, or persistent cough without colds in the past 12 months), and 2 children had no history of respiratory symptoms. Children were asymptomatic on the day of the test and had no history of

Results

Eighteen children completed both a shortened and a standard inhaled AMP challenge. The mean time elapsed between tests was 16 ± 11.4 days (range, 7 to 42 days). Three children undertaking protocol 1 did not complete the standard (nine-step) challenge and were excluded from further analysis. Reasons for noncompletion were exacerbation of symptoms in the period preceding the AMP challenge (n = 1) or premature termination of the challenge arising from poor subject cooperation (n = 2).

All children

Discussion

The present study has demonstrated that the combined use of FOT and shortened AMP challenge is feasible in young children. Importantly, we demonstrated a high degree of concordance in responsiveness between a shortened challenge and the standard AMP protocol. Further, we demonstrated that the shortened challenge was repeatable for determining BHR to AMP. Interestingly, the majority of children responded with an increase in Rrs8 either alone (> 47%) or in combination with audible wheeze (> 33%),

Acknowledgment

The authors would like to acknowledge the assistance of Dr. K. Udomittipong for her assistance in performing the AMP challenge tests.

References (20)

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This study was funded by the Asthma Foundation of Western Australia.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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