Taken together, the available data on upper respiratory samples pooling for screening SARS-CoV-2 infection would allow to draw some ad interim conclusions. First and foremost, this strategy shall only be used in areas with limited prevalence of SARS-CoV-2 infection (i.e. typically <5%), for population screening and not for diagnostic investigation of highly suspected or symptomatic cases. The pools shall then be prepared using clinical specimens, preferably nasopharyngeal samples (or saliva), and must not be made with extracted viral RNA. It is then extremely important that the local NAAT has been thoughtfully validated for purposes of pool testing, thus displaying adequate analytical sensitivity, and preferably encompassing RNA extraction rather than employing rapid molecular assays. As concerns the number of individual specimens, current evidence would support the use of pools made of not more than 5 upper respiratory samples, since this value seems to combine significantly improved efficiency with unvaried diagnostic sensitivity. The presence of interfering substances (e.g., antiviral drugs, cell-free hemoglobin, and so forth) shall always be ruled out, traceability (preferably automatic) to individual samples must be ensured and, finally, a second aliquot shall always be available for being individually tested when pool screening is positive.
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