Abstract
We conducted a systematic review and meta-analysis to investigate the possible difference in the SARS-CoV-2 viral load between asymptomatic and symptomatic COVID-19 patients. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in abstracting data and assessing validity. We searched MEDLINE, Scopus, Web of Science and Google Scholar for all investigations in the English language, reporting data on the threshold cycle (Ct) from real-time RT-PCR assays for the RNA-dependent RNA polymerase (RdRp), envelope (E) and nucleocapsid (N) SARS-CoV-2 genes in asymptomatic and symptomatic COVID-19 patients. Results: Overall, 703 COVID-19 patients (553 symptomatic and 150 asymptomatic) were analyzed. Five investigations reported the mean age of patients, evidencing that asymptomatic patients were younger than symptomatic patients (34.0 vs. 40.3 years, respectively). Pooled data regarding the levels of expression of the RdRp gene revealed no significant difference between symptomatic and asymptomatic subjects. Similarly, no differences were observed comparing the mean Ct values for the E and N genes. Based on real-time RT-PCR data, no differences exist in the viral load between symptomatic and asymptomatic COVID-19 subjects considering Ct values for RdRp, E and N genes’ expression. Asymptomatic subjects may represent a reservoir of the infection and significantly contribute to the maintenance of the pandemic.
Highlights
Since the beginning of the COVID-19 pandemic, SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) testing has played a pivotal role in both diagnosis and epidemiological analyses worldwide [1]
I2 = 0 indicated no heterogeneity, while we considered low, moderate and high degrees of heterogeneity based on the values of I2 of
World Health Organization (WHO), the RNA-dependent RNA polymerase (RdRp), E and N genes represent the targets for the detection of SARS-CoV-2, the E gene for first-line screening, the RdRp gene for the confirmatory assay and the N gene for the additional confirmatory assay [15]
Summary
Since the beginning of the COVID-19 pandemic, SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) testing has played a pivotal role in both diagnosis and epidemiological analyses worldwide [1]. RT-PCR assays generally target the RNA-dependent RNA polymerase (RdRp), envelope protein (E) or nucleocapsid protein (N) genes [2]. As it has been demonstrated since the early stage of the outbreak, the spread of SARS-CoV-2 infection has been largely maintained by asymptomatic individuals [3,4,5]. Some investigations analyzing the dynamic of COVID-19 transmission have reported no differences in viral loads between asymptomatic and symptomatic patients, determining substantial containment challenges [5]. The aim of the present study was to determine the existence, if any, of different viral loads between symptomatic and asymptomatic COVID-19 patients, conducting a meta-analysis based on the available data published in the literature
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