PURPOSE: To evaluate aerosolized bronchodilator (BD) therapy effectiveness, the American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines treat FVC and FEV1 equally and require fixed increases in both volume (≥200 mL) and percentage (≥12%). Differently, we propose a statistical approach which compares three pre- and three post- BD spirometric trials for each patient and avoids fixed increases.
METHODS: After Institutional Review Board approval, we retrospectively analyzed one-year's pre-and post-BD forced spirometric trials for 313 consecutive clinical laboratory studies meeting ATS/ERS quality standards. We compared changes in FEV1, FEV3, and FVC from three pre-BD and three post-BD trials. Each study was classified as responsive or not according to ATS/ERS guidelines and independently according to our new individualized statistical approach. Primarily, our positive response required a statistically significant FEV1 improvement by an unpaired, single-tailed t-test at p<0.05 plus a similar improvement in FEV3 or FVC.
RESULTS: 135 studies were guideline and t-test non-responsive (true negative), 86 were guideline and t-test responsive (true positive), 89 were guideline non-responsive and t-test responsive (false negative) and 3 were guideline responsive and t-test non-responsive (false positive). Thus ATS/ERS guidelines missed more responders than they identified, especially patients with FEV1 <0.75L or >3.0L. The three false positive responders had large post-BD increases in FVC due to increased expiratory times without ATS/ERS or statistically significant increases in FEV1. Secondarily, FEV1 rank order statistics at p=0.05 agreed with t-tests 312/315 times.
CONCLUSION: ATS/ERS guidelines failed to detect positive bronchodilator response in 89 of 175 responders detected by an undemanding statistical analyses comparing pre- and post-BD measurements. More severely obstructed patients were especially penalized because they could not meet the ATS/ERS volume criteria.
CLINICAL IMPLICATIONS: This new statistical approach better informs clinicians of bronchodilator effectiveness.
DISCLOSURE: James Hansen, None.