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Reply to Letter to the Editor: “Characteristic CT findings distinguishing 2019 novel coronavirus disease (COVID-19) from influenza pneumonia”

by Bin Song (songbin@fudan.edu.cn)

Characteristic CT findings distinguishing 2019 novel coronavirus disease (COVID-19) from influenza pneumonia

Dear readers,

We express our sincere thanks to you. Thank you for your interest in our work.

This is a retrospective study in our center. As we know, the first confirmed COVID-19 case was reported in Wuhan, China. Then, the outbreak spread throughout the whole country. In our center, the first confirmed case was diagnosed on January 16, 2020. Only 13 confirmed cases were diagnosed until February 25, 2020 (our submission date) in our center. We admitted very few COVID-19 cases in our final study. Additionally, all influenza pneumonia cases were consecutively enrolled in our study. We excluded some cases including negative CT findings and other diagnosis (lung tuberculosis, pneumonedema, mucous plug combined with atelectasis, bronchitis, breathing motion artifact, tuberculosis and bronchiectasis combined with infection). A total of 92 patients with influenza pneumonia were enrolled in our final study. We described our exclusion criteria in method section.

All influenza pneumonia cases were not tested for COVID-19 before January 2020. All suspicious cases including influenza pneumonia were tested after the first reported COVID-19 confirmed case in Shanghai, China. We are not sure that the cases are co-infected COVID-19 before the pandemic.

This study was retrospective in design, especially for the influenza pneumonia cohort. Most patients did not undergo CT scanning, leading to a selection bias and therefore undermining the validity of the results. We also presented the limitation in our discussion section. Nevertheless, the results were encouraging and should be used to generate hypotheses for future large-scale multicenter studies using CT to distinguish COVID-19 from other forms of viral pneumonia. As we know, influenza and COVID-19 have some similar clinical presentation and lab test results. Our study was aimed to investigate the capability of CT in differentiating COVID-19 from influenza pneumonia.

The pandemic has become global health event and influenced the global economy. However, we passionately believe we will overcome the pandemic. Also, we believe CT can play an important role in the diagnosis of COVID-19.

Thanks again for your comments. We hope we will discuss the related topics in future.