Meta-analysis
Five studies that reported the mean and standard deviation of the Ct value or the value could be calculated from other reported data in the study were included in the meta-analysis. The RevMan 5.4.1 was used for analysis. There was a high level of heterogeneity in the mouthwash type, diagnostic kit, specimen (saliva or nasopharynx or oropharynx swab) and time of experiment (the time between the first RT-PCR test and using the mouthwash) among studies. Random-effects models and subgroup analysis were used to reduce the impact of heterogeneity. The Egger’s and Begg’s tests were used for publication bias assessment.