The INPULSIS trials of idiopathic pulmonary fibrosis treatment: explaining further discrepancies on exacerbations

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In a recent paper on the INPULSIS trials, two duplicate 1-year randomised controlled trials evaluating nintedanib in the treatment of idiopathic pulmonary fibrosis (IPF) [1], we provided the methodological explanation for the apparent inconsistent results arising from the two different definitions of exacerbations used in those studies [2]. These trials reported vastly different findings in their pooled analysis [1]. Indeed, the risk of an investigator-reported acute exacerbation was lower by 36% with nintedanib compared with placebo but not statistically significant (p=0.08), while, after adjudication according to a complex definition involving multiple criteria, the risk was lower by 68% and statistically significant (p=0.001). We explained that such differences in risk reductions and in statistical significance are simply the result of including outcome events that are not actual exacerbations, leading to the phenomenon of treatment effect dilution and false nonsignificant effects [2]. The correct risk reduction of 68% based on the accurate adjudicated events is diluted to a less impressive and now nonsignificant risk reduction of 36% when “false” events were added in the same proportion to both groups.