To the Editor:
We highly appreciate the colleagues’ interest and comments regarding our meta-analysis,1 and fully agree that there is a potential risk of bias due to data redundancy.
We would like to point out that not all data sources that served to constitute the database for this meta-analysis specified the period of patient recruitment, age, admitted hospital, or other parameters that could allow the reliable exclusion of duplicates. As all the data from the published papers were anonymized, exclusion of duplicates was ultimately not possible. The included studies originate from several countries, and for all countries from which only one study was included, it is very likely that no patient was included twice in the meta-analysis.
In this context, the greatest risk of bias is associated with studies from China and, in particular, with data from the primary outbreak region. At the time of data extraction for meta-analysis, we carefully cross-checked that the respective studies originated from different hospitals to exclude an overlap of the primary data. In some studies, pooled data from several hospitals were analyzed. Herein, as noted, an overlap cannot be excluded with 100% certainty.
It should be noted that the present analysis is one of the first large meta-analysis on a highly dynamic and new disease entity. Moreover, we only used data from peer-reviewed publications to ensure a high-quality database. Consequently, publications from preprint servers were also excluded. Therefore, we believe that despite possible overlaps in a very small proportion of the studies included, the present meta-analysis was only marginally affected. However, the comments of Tang et al.2 are pertinent and should receive attention and be considered in the context of future meta-analyses.
Declaration of competing interest
PD Dr. Raimann: received funding and speaker honoraria from Boehringer Ingelheim, pharma-consult Petersohn, HemoSonics, Publikationsfond Uni Frankfurt, Keller Medical GmbH and HELIOS Klinikum.
The other authors have no conflicts of interest to declare.
References
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