Yield of a mannitol bronchial provocation test (BPT) for the diagnosis of asthma in a real-life study

Abstract

Introduction: The inespecific bronchial provocation tests (BPT) used to assess bronchial hyperresponsiveness may be direct or indirect. Methacholine is the most frequently used agent for direct BPT, and mannitol for indirect BPT. Patients and Methods: Descriptive, retrospective, observational study of 100 patients who, due a doubtful asthma diagnosis, underwent a BPT with mannitol as part of the diagnostic algorithm for asthma between January 2011 and November 2014. Results: Mean age was 37.2 (r: 17-69) years. Thirty-four patients (34%) were male and 66 (66%) female. FVC was 88.1% (r: 46-126), FEV1 97.3% (r: 60-130), FEV1/FVC 88.4% (r: 42-131). Seventy-five (75%) were diagnosed with asthma. Mannitol BPT was positive in 57 patients (57%) and negative in 43 (43%). The methacholine BPT was positive in 62 patients (62%) and negative in 38 (38%) patients. In the 75 asthma patients, mannitol BPT was positive in 55 (sensitivity (S): 73.3%) and methacholine BPT was positive in 57 (S: 76%). In the 25 (25%) non-asthma patients, mannitol BPT was negative in 23 (specificity (Sp): 92%) and methacholine BPT was negative in 20 (Sp: 80%) (Table 1). Mannitol BPT had a positive predictive value (PPV) of 96.5% and an NPV of 53.5%. Methacholine BPT had a positive predictive value (PPV) of 91.9% and an NPV of 52.6%. Conclusions: In a real-life study the mannitol test seems to show greater specificity and greater positive predictive value than the methacholine test for establishing the diagnosis.