@article {Tran1800376, author = {Tanja Tran and Samy Suissa}, title = {The effect of anti-acid therapy on survival in idiopathic pulmonary fibrosis: a methodological review of observational studies}, elocation-id = {1800376}, year = {2018}, doi = {10.1183/13993003.00376-2018}, publisher = {European Respiratory Society}, abstract = {Background: International treatment guidelines for idiopathic pulmonary fibrosis (IPF) give a conditional recommendation for anti-acid therapy. As some observational studies reported discrepant findings on the effectiveness of anti-acid therapy on mortality in IPF, we reviewed all studies to evaluate whether immortal time bias explains these discrepancies.Methods: We searched the EMBASE AND MEDLINE databases until July 2017 for observational studies assessing the effectiveness of anti-acid therapy on mortality in IPF. Hazard ratios of mortality with anti-acid therapy were pooled across studies using random-effect models, stratified by the presence of immortal time bias.Results: We identified 10 observational studies. Four of the five studies reporting beneficial effects of anti-acid therapy use on mortality were affected by immortal time bias (pooled hazard ratio 0.46; 95\% CI 0.30{\textendash}0.69), while the fifth was unclear. The five studies that avoided immortal time bias reported no effect of anti-acid therapy on mortality (pooled hazard ratio 0.99; 95\% CI 0.81{\textendash}1.22).Conclusion: The apparent beneficial effects of anti-acid therapy on mortality in patients with IPF result from observational studies affected by immortal time bias. The effectiveness of anti-acid therapy in IPF thus remains uncertain and needs to be reassessed with more accurate observational study methods and randomised trials.Immortal time bias explains apparent effectiveness of anti-acid drugs on mortality in idiopathic pulmonary fibrosisFootnotesThis manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.Conflict of interest: Ms. Tran has nothing to disclose.Conflict of interest: Dr. Suissa has nothing to disclose.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/early/2018/04/26/13993003.00376-2018}, eprint = {https://erj.ersjournals.com/content/early/2018/04/26/13993003.00376-2018.full.pdf}, journal = {European Respiratory Journal} }