SARS-CoV-2 identification and IgA antibodies in saliva: one sample two tests approach for diagnosis

Aita, Ada; Basso, Daniela; Maria Cattelan, Anna; Fioretto, Paola; Navaglia, Filippo; Barbaro, Francesco; Stoppa, Alice; Coccorullo, Enrico; Farella, Assunta; Socal, Aurora; Vettor, Roberto; Plebani, Mario

Aim This study aims to verify whether standardized saliva collection is suitable for SARS-CoV-2 molecular detection and IgA measurement. Methods 43 COVID-19 inpatients and 326 screening subjects underwent naso-pharyngeal (NP)-swab and saliva collection (Salivette). Inpatients also underwent repeated blood collections to evaluate inflammation and organs involvement. In all patients and subjects, SARS-CoV-2 (gene E) rRT-PCR was undertaken in saliva and NP-swabs. Salivary IgA and serum IgA, IgG, IgM were measured on inpatients’ samples. Results NP-swabs and saliva were both SARS-CoV-2 positive in 7 (16%) or both negative in 35 (82%) out of 43 patients successfully included in the study. NP-swabs and saliva results did not perfectly match in one patient (saliva positive, NP-swab negative). Positive molecular results were significantly associated with disease duration (p=0.0049). 326/326 screening subjects were SARS-CoV-2 negative on both NP-swabs and saliva. Among the 27 saliva samples tested for IgA, 18 were IgA positive. Salivary IgA positivity was associated with pneumonia (p=0.002) and CRP values (p=0.0183), not with other clinical and molecular data, or with serum immunoglubulins. Conclusions A standardized saliva collection can be adopted to detect SARS-CoV-2 infection in alternative to NP-swabs. Preliminary data on salivary IgA support the use of saliva also for patient monitoring.