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November 28, 2001

Influence of Methodological Quality on Study Conclusions—Reply

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorJody W.ZylkeMD, Contributing EditorIndividualAuthor

JAMA. 2001;286(20):2544-2547. doi:10.1001/jama.286.20.2542

In Reply: Dr Liberati and colleagues and Dr Sánchez García point out an error in the "Results" section of our article. The data in Table 2 are based on our initial analyses, which we revised during the review process. We apologize for the confusion. The correct data are presented in Table 1. The chosen cutoff for low- and-high-quality studies is, of course, arbitrary, but the data in Table 1 clearly show that there was no reason for choosing a cutoff point on a post hoc basis. In contrast to the opinion of Liberati et al, we think that SDD studies are very appropriate to explore the relationship between study quality and observed effects. As opposed to mortality, the end point of pneumonia is rather weak since establishing this diagnosis is extremely difficult. Therefore, this end point is prone to investigator bias, which is consistent with our findings. At no point did we claim that only RCTs were included.