When Should a Reversibility Test Be Performed on Patients with Early Stages of Asthma and Normal Spirometry?

Abstract

Subjects with bronchial asthmatic symptoms, forced expiratory volume in 1 second (FEV₁) and FEV₁/forced vital capacity [FVC] > 80% could show a positive reversibility test with salbutamol in about 25% of the cases. The aim of this study was to evaluate if a limit functional value for spirometry exists where a reversibility test using salbutamol, over this limit, is not necessary to confirm the diagnosis of asthma. Four hundred patients (mean age 31.12 ± 10.99) with asthmatic symptoms and normal spirometry (mean FEV₁ 96.06 ± 11.82%, mean FEV₁/FVC 98.89 ± 6.03%) were recruited. The number of subjects with reversible airflow obstruction (RAO) was evaluated using the following different criteria of reversibility: FEV₁ and FVC ≥ slant 12%, peak expiratory flow (PEF) ≥ slant 15%, FEF_{25 −75} ≥ slant 35%, and at least one of these (ANY). In subjects with baseline FEV₁ > 100% (150 patients), 26 (17.3%) patients showed a FEV₁ increase > 12% and, among the criteria used, 45 patients (30%) showed ANY. In subjects with baseline FEV₁/FVC > 100% (204 patients), 36 patients (17.6%) showed a FEV₁ increase > 12% and 53 patients (26.8%) showed ANY. In subjects with baseline FEF_{25 −75} > 70% (209 patients), 26 (12.44%) and 49 (23.44%) patients, respectively, showed an increase in FEV₁ > 12%, and ANY. In 56 patients with baseline cut-offs (evaluated together) FEV₁ > 100%, FEV₁/FVC > 100% and FEF₂₅₋₇₅ > 70%, 10 patients (17.85%) showed a RAO with ANY. FEV₁ > 121% or FEV₁/FVC > 110.8% or FEF_{25 −75} > 110% were cut-off values identified in this study where no RAO subjects were found over these limits. In conclusion, baseline FEV₁ > 100%, FEV₁/FVC > 100% and FEF_{25 −75} > 70% cannot be considered cut-offs where it is not necessary to perform a reversibility test with a bronchodilator over these limits. It is improbable to find a positive reversibility test using salbutamol in patients with asthmatic symptoms and FEV₁ > 121% or FEV₁/FVC > 110.8% or FEF_{25 −75} > 110% to confirm the diagnosis of asthma.