Factors associated with mortality in patients with COVID-19. A quantitative evidence synthesis of clinical and laboratory dataThe COVID-19 pandemic caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2) has become a serious challenge for health systems worldwide. Despite the favorable clinical course for most cases, a mortality rate of 30-70% is expected for COVID-19 patients treated on intensive care unit (ICU) [1]. Reports have shown an increased risk of death for older patients with existing comorbidities and potential biomarkers associated with severity for COVID-19 patients [2,3].Because of the complexity and the limited evidence on the pathogenesis of COVID-19, the management of critically ill patients has been challenging. Multiple recent studies have provided valuable clinical and laboratory features of hospitalized patients with COVID-19, but in many of them the information is not complete and there is a potential for overlapping data. Therefore, findings from a comprehensive systematic review can help physicians to understand the disease and make decisions for critically ill patients. In this study, we performed a quantitative evidence synthesis of clinical and laboratory factors associated with mortality in patients with COVID-19.We searched the peer-reviewed (PubMed, Web of Science, Scopus, Embase) and gray (Google Scholar, bioRxiv, medRxiv) literature to identify studies comparing clinical data, laboratory parameters (hematological, biochemical, inflammatory markers, coagulation factors, and blood gas analysis) and complications between non-survivors and survivors of COVID-19. We included only studies providing clinical data and at least one of the laboratory parameters previously mentioned. We excluded publications with potential overlapping reports, and studies from which data extraction was not possible. In case of potential overlapping data, we selected the study with most complete information.Reports were screened in two stages: screening of titles and abstracts followed by the retrieval and screening of full-text articles. Searches were performed from January 1, 2020 up to April 06, 2020, without language restrictions. The reference lists of all eligible studies and reviews were also evaluated to identify additional studies for inclusion. The following search terms were used: "COVID-19″, "severe acute respiratory syndrome coronavirus 2″, "SARS-CoV-2″, "2019-nCoV", "coronavirus" and "coronaviruses".Data from publications were extracted by two authors and crosschecked for accuracy. Our outcome of interest was in-hospital death. Clinical data, laboratory parameters, and complications were considered predictor variables. Effect sizes were reported as mean difference (MD) or standardized mean difference (SMD) for continuous variables and risk ratio (RR) for dichotomous variables with 95% confidence intervals (CI). Not all studies reported data on all predictor variables, and the pooled analysis was estimated from the data available for each variable. A random-effects model was used to poo...
