SESSION TITLE: Asthma Posters I
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 29, 2014 at 01:30 PM - 02:30 PM
PURPOSE: Methacholine challenge testing (MCT) has been the primary test used to identify non-specific airway hyperresponsiveness (AHR) related to either asthma or exercise-induced bronchospasm (EIB). Inhalation mannitol has been demonstrated to be a more accurate predictor of underlying asthma based on its properties. We compared mannitol vs. MCT in a group of individuals, primarily military with normal baseline spirometry.
METHODS: Patients referred for MCT underwent repeat bronchoprovocation testing with mannitol no sooner than 48 hrs post MCT. Methacholine was administered with increasing dosages to 16 mg/ml or PC20 and mannitol was given with increasing dosages to 160 mg/ml or PC15 per guidelines. Impulse oscillometry (IOS) resistance values (R5, R20, X5) were recorded at baseline and after maximum dose during each study.
RESULTS: A total of 39 patients have completed both testing modalities. The group is 72% males with mean age of 35.4 ±10.8 years. Mean baseline spirometry values included: FEV1(% pred): 93.2±12.5; FVC(% pred): 95.0±11.6; and FEV1/FVC = 80.2±6.5. There were 8 positive and 31 negative MCT studies, while only 7 reactive mannitol with 32 negative studies. Only 50% of positive MCT correlated with a reactive mannitol. IOS resistance values (R5 and X5-X5pred) post MCT showed significant changes for positive studies (p =0.05) while mannitol values were non-significant.
CONCLUSIONS: Discussion: There is a clear discordance with reactive MCT and mannitol in this population with normal spirometry being evaluated for exertional dyspnea. Currently, there is no trend in this study favoring one methodology for determining AHR vs inflammation as the underlying mechanism for symptoms. The use of IOS resistance values did not help discriminate positive studies especially with mannitol. Conclusions: In a military population evaluated for exertional dyspnea, reactive MCT indicates underlying AHR alone favoring the diagnosis of EIB while the remaining 50% may have underlying inflammation c/w asthma.
CLINICAL IMPLICATIONS: Methacholine should remain a primary testing modality to evaluate for non-specific AHR especially in military personnel to diagnose EIB. Further comparison is warranted between modalities.
DISCLOSURE: The following authors have nothing to disclose: Michelle Alders, Heather Arellano, Jackie Hayes, Michael Morris
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