Importance of excluded duplicates reporting in a systematic review

Xi Zhang · Jiang-Hui Hong-Cai

We read with great interest the review article by Ghodsi and colleagues (Volume 17, issue 3) [ 1]. The authors aimed to evaluate the chest computed tomography (CT) findings in infants with confirmed coronavirus disease 2019 (COVID-19) infection. Certainly, the findings of Ghodsi et al. hold significance for physicians when determining the typical characteristics of COVID-19. While agreeing with the conclusions made by the authors, we would like to draw their attention to a certain aspect.

It is a pity that the authors did not extract the hospital’s name and recruitment periods because some infants may have been included in multiple publications, as admission dates overlap for reports from the same hospital. A total of 35 articles involving 70 infants with COVID-19 were included in this study. The children included in the seven articles [ 2- 8] were all from Wuhan Children’s Hospital,diagnosed with COVID-19 between 14 December 2019 and 22 March 2020. The CT results of a 10-month-old female infant mentioned in Cai et al. [ 2] and Du et al. [ 3] all showed bilateral abnormalities, which may describe the same infant.Of note, the 12-month-old boy described by Du et al. [ 3], Li et al. [ 5], and Xia et al. [ 8]. Also could be the same person.The authors should exclude studies suspected of including duplicate reporting as duplication can give a potentially biased picture.

Isolated case reports and repeat case series from the same hospital/region should be excluded to avoid duplicate data from large retrospective studies. Including duplicates in a review may create an inaccurate scientific record and may affect understanding the disease and its epidemiology [ 9].Studies suspected of including duplicate reporting can be identified based on hospital location, recruitment periods and characteristics of the participants (e.g., demographic information, clinical symptoms, laboratory results, treatments, clinical outcomes). Although duplicate reporting has small numbers in this systematic review and a reanalysis is not likely to change the results, we humbly suggest that the authors extract the setting/hospital and recruitment periods.If a hospital had published its cases more than once, as when recruitment periods overlapped, only the most informative study with the larger sample size that met the inclusion criteria should be included to minimize the possibility of double counting [ 10].

Author contributions CJH and ZHX drafted and revised the manuscript. All authors read and approved the final manuscript.

Funding This manuscript did not receive any funding.

Compliance with ethical standards

Ethical approval Not applicable.

Conflict of interest No financial or nonfinancial benefits have been received or will be received from any party related directly or indirectly to the subject of this article. The authors have no conflict of interest to declare.

Data availability Not applicable.