, Volume 28, Issue 7, p 872
Date: 04 Apr 2013

Community-Acquired Pneumonia and Proton Pump Inhibitors

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To the Editors:—We read with interest the article by Jena and colleagues regarding the possibility of residual confounding in the association of proton pump inhibitors (PPIs) and community-acquired pneumonia (CAP).1 Specifically, we appreciated the argument for “falsification analysis,” which Jena has discussed elsewhere.2

The notion that a hypothesized causal relationship between an exposure and one outcome can be weakened or strengthened by observing whether the exposure is associated with various other “implausible” outcomes has previously been described as the “specificity” criterion for causality. Notably, this criterion has a long and debated history of use in epidemiological research.3 We agree with the authors that it deserves further attention in causal interpretations of observational data.

However, this method cannot replace other standard considerations in observational data analysis. For example, in this study, the authors base their conclusions about confounding on an assoc ...