SESSION TITLE: Signs and Symptoms of Chest Diseases Posters
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM
PURPOSE: Exercise-induced bronchoconstriction (EIB) is a common condition among young individuals who present to the outpatient clinic for exertional dyspnoea. Diagnosis of EIB requires exercise testing for asthma (EIA) which is the current gold standard investigation in our centre, but there are other alternatives such as methacholine (MCT) and hypertonic saline (HS) challenge tests. Each test has its advantages and disadvantages.
METHODS: Participants were recruited prospectively between May 2012 and December 2014 for the HS study (S1). MCT data were obtained using a retrospective study of patients who underwent both MCT and EIA testing from January to December 2013 (S2). The 3 tests were carried out according to European Respiratory Society (ERS)/ American Thoracic Society (ATS) guidelines. MCT was considered positive if PC20<8mg/ml. HS testing was performed using nebulised 4.5% NaCl, and considered positive if there is a fall in FEV1 of 15% or more. Provocative doses of HS causing a 15% fall in FEV1 were calculated (PD15). Participants of S1 were surveyed on which test they preferred. The sensitivity, specificity and accuracy of each diagnostic test were calculated using EIA as the gold standard.
RESULTS: 32 patients were included in S1 (age 21.6 ±6.4 years , 93.8% males, PC20 7.76 ± 6.94 mg/ml, PD15 16.46±14.98 ml), and 174 subjects in S2 (age 19.4 ± 4.0 years, 97.1% males, PC20 7.58 ± 6.76 mg/ml). S1 results were: 46.9% positive EIA tests, and HS sensitivity of 80.0%, specificity of 70.6%, and accuracy of 75.0%. Surveys indicated that 46.9% of patients preferred HS testing over EIA.S2 results were:37.9% positive EIA tests, and MCT sensitivity of 84.8%, specificity of 61.1%,and accuracy of 70.1%.
CONCLUSIONS: Hypertonic saline has higher overall accuracy and specificity in predicting EIA compared to MCT. However, MCT has better sensitivity compared to HS.
CLINICAL IMPLICATIONS: MCT is useful in ruling out EIB when it is negative. A positive MCT should be followed by HS which has higher specificity for EIB. Both tests can be used as an alternative to EIA in laboratories without exercise equipment.
DISCLOSURE: The following authors have nothing to disclose: Jessica Tan, Wui Mei Chew, Mariko Koh, Chian Min Loo, Gan Liang Tan, Therese Lappere
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