Rectal shedding of SARS-CoV-2 in patients with negative COVID-19 nasopharyngeal RT-PCR test

BackgroundCOVID-19, caused by the novel coronavirus SARS-CoV-2, was first identified in China in December 2019 and rapidly spread worldwide, primarily affecting the respiratory system. Although RT-PCR on nasopharyngeal swabs is the standard diagnostic method, emerging evidence suggests that SARS-CoV-2 RNA may be detected in rectal swabs even if respiratory samples test negative.ObjectiveTo assess the ability of rectal swabs to detect SARS-CoV-2 viral shedding in participants with negative nasopharyngeal swabs.MethodAdult patients scheduled for colonoscopy at Mater Dei Hospital between June 2020 and April 2021 were enrolled. All participants had a confirmed negative nasopharyngeal swab for SARS-CoV-2 by RT-PCR within 72 h before enrolment and provided informed consent. Data on demographics, epidemiology and clinical symptoms were collected through structured interviews and medical record reviews. Prior to colonoscopy, rectal swabs were obtained and all samples were processed following standardised laboratory protocols.Results200 participants were enrolled. None of the patients had prior COVID-19 history. 7.5% (n = 15) tested positive on rectal swabs despite having a negative nasopharyngeal swab in the preceding 72 h.ConclusionWhile combining nasopharyngeal and rectal swab sampling may improve COVID-19 diagnosis, routine use of both methods might not be cost-effective. Nonetheless, rectal swabs could prove beneficial for symptomatic patients with negative nasopharyngeal results or those with known exposure to COVID-19.