RECTAL SWABS FOR COVID-19 DIAGNOSIS
the oro-fecal route is well-documented in patients affected by SARS-Cov-19 (Wang et al., 2020; Guan et al., 2020; Lescure et al., 2020). In particular, fecal excretion persisted for 1‐11 days after sputum excretion in 23%‐82% adults (Tian et al., 2020). Oropharyngeal specimen negativity been described together with anal swab positivity up to 28 days after the onset of symptoms also in in children (Xu et al., 2020; Fan et al., 2020). This finding suggests that some patients with SARS-CoV-2 infection have viral RNA or live infectious virus in feces well after the negativization of oropharyngeal specimens.
Apart from the inference that patients test positive on rectal swabs even after nasopharyngeal swabs become negative, another deduction can be drawn that is even more important by an operative standpoint. Indeed, the available data suggest that some patients test positive on rectal swabs in the very first days of COVID-19 onset (Lescure et al., 2020). To make a few examples, in a review article, Tian et al. (2020) reported fecal PCR positivity 2‐5 days after sputum in in 36%‐53% of patients, while Xiao et al (2020) found that 39/73 hospitalized patients had viral RNA in their feces from 1 to 12 days. Therefore, the occurrence of oro-fecal route points towards the usefulness of rectal swabs at the very onset of the disease to confirm, or even diagnose, COVID-19. A rectal swab could be performed, also in absence of digestive symptoms, in persons who meet one of the two following criteria:
1) throat- or sputum-negative patients with symptoms, signs or instrumental exams that are suspicious for COVID-19;
2) throat- or sputum-negative subjects with close or casual contacts with confirmed cases.
1) Fan Q, Pan Y, Wu Q, Liu S, Song X, et al. 2020. Anal swab findings in an infant with COVID‐19. Pediatric Investigation, 4 (1), https://doi.org/10.1002/ped4.12186.
2) Lescure FX, Bouadma L, Nguyen D, Parisey M, Wicky PH, et al. 2020. Clinical and virological data of the first cases of COVID-19 in Europe: a case series. Lancet Infect Dis., pii: S1473-3099(20)30200-0. doi: 10.1016/S1473-3099(20)30200-0.
3) Xiao F, Tang M, Zheng X, Liu Y. 2020. Evidence for Gastrointestinal Infection of SARS-CoV-2. Gastroenterology, in press. DOI: https://doi.org/10.1053/j.gastro.2020.02.055.
4) Xu Y, Li X, Zhu B, Liang H, Fang C, et al. 2020. Characteristics of pediatric SARS-CoV-2 infection and potential evidence for persistent fecal viral shedding. Nat Med., 26(4):502-505. doi: 10.1038/s41591-020-0817-4.
5) Tian Y, Rong L, Nian W, He Y. 2020. Review article: gastrointestinal features in COVID-19 and the possibility of faecal transmission. Aliment Pharmacol Ther. 2020 May;51(9):843-851. doi: 10.1111/apt.15731.
6) Wang W, Xu Y, Gao R, Lu R, Han K, et al. 2020. Detection of SARS-CoV-2 in Different Types of Clinical Specimens. JAMA. 2020 Mar 11. doi: 10.1001/jama.2020.3786.
Division of Respiratory and Allergic Diseases, Department of Chest Diseases, High Specialty A. Cardarelli Hospital, Napoli, Italy
Medical School of Specialization in Respiratory Diseases, University on Naples Federico II
University of Naples Federico II, Naples, Italy
Department of Translational Medical Sciences
Competing interests: No competing interests