Validation of saliva sampling as an alternative to oro-nasopharyngeal swab for detection of SARS-CoV-2 using unextracted rRT-PCR with the Allplex 2019-nCoV assay

Abstract

Introduction. The current severe acute respiratory syndrome-associated coronavirus-2 (SARS-CoV-2) pandemic has stressed the global supply chain for specialized equipment, including flocked swabs. Hypothesis. Saliva could be a potential alternative specimen source for diagnosis of SARS-CoV-2 infection by reverse-transcriptase PCR (RT-PCR). Aim. To compare the detection efficiency of SARS-CoV-2 RNA in saliva and oro-nasopharyngeal swab (ONPS) specimens. Methodology. Patients recruited from hospital provided paired saliva and ONPS specimens. We performed manual or automated RT-PCR with prior proteinase K treatment without RNA extraction using the Seegene Allplex 2019 nCoV assay. Results. Of the 773 specimen pairs, 165 (21.3 %) had at least one positive sample. Additionally, 138 specimens tested positive by both sampling methods. Fifteen and 12 cases were detected only by nasopharyngeal swab and saliva, respectively. The sensitivity of ONPS (153/165; 92.7 %; 95 % CI: 88.8–96.7) was similar to that of saliva (150/165; 90.9 %; 95 % CI: 86.5–95.3; P=0.5). In patients with symptoms for ≤ 10 days, the sensitivity of ONPS (118/126; 93.7 %; 95 % CI: 89.4–97.9) was similar to that of saliva (122/126; 96.8 %; 95 % CI: 93.8–99.9 %; P=0.9). However, the sensitivity of ONPS (20/22; 95.2 %; 95 % CI: 86.1–100) was higher than that of saliva (16/22; 71.4 %; 95 % CI: 52.1–90.8) in patients with symptoms for more than 10 days. Conclusions. Saliva sampling is an acceptable alternative to ONPS for diagnosing SARS-CoV-2 infection in symptomatic individuals displaying symptoms for ≤ 10 days. These results reinforce the need to expand the use of saliva samples, which are self-collected and do not require swabs.