Saliva Is a Sensitive and Accessible Sample Both for SARS-CoV-2 Detection and for the Evaluation of Treatment Effectiveness in Follow-Up Studies

Abstract

Despite emerging evidence indicating that molecular SARS-CoV-2 tests performed on saliva have diagnostic sensitivity and specificity comparable to those observed with nasopharyngeal swabs (NPSs), most in vivo follow-up studies on the efficacy of drugs against SARS-CoV-2 have been performed on NPSs, not considering saliva as a possible alternative matrix. For this reason, in this study, we used, in parallel, saliva and NPS samples for the detection of SARS-CoV-2 by real-time RT-PCR in patients receiving Tixagevimab/Cilgavimab, Nirmatrelvir/Ritonavir, or Sotrovimab as a treatment against SARS-CoV-2. Our results showed a good correlation between the NPS and saliva samples for each drug; moreover, comparable changes in the cycle threshold (Ct) levels in saliva and NPSs were observed both 7 days and 30 days after treatment, thus confirming that the saliva represents a good matrix for in vivo follow-up studies verifying the effectiveness of treatments against SARS-CoV-2.

Keywords: COVID-19 diagnosis; SARS-CoV-2; antiviral therapy; follow-up studies; molecular assay; monoclonal antibodies; saliva.

Figure 1

Linear regression analysis in NPS and saliva samples in patients receiving Tixagevimab/Cilgavimab (A), Sotrovimab (B), or Nirmatrelvir/Ritonavir (C).

Figure 2

Mean of Ct reduction in saliva samples (A) and NPSs (B) at T0, T7, and T30, compared to T0, according to the three different treatments. SEM: standard error of the mean. Tixagevimab/Cilgavimab in blue, Sotrovimab in green, and Nirmatrelvir/Ritonavir in red.