Diagnostic performance of saliva RT-PCR test as a diagnostic tool and its utility in the detection of SARS-CoV-2 shedding with different patient characteristics: Prospective observational study

Background: Salivary shedding of SARS-CoV-2 is a known entity and its role has been established in transmission of the disease. The present study was performed to evaluate the duration of viral shedding in saliva in COVID-19 patients and its variation among symptomatic and asymptomatic patients with or without co-morbidities.Methods: The present prospective observational study was conducted at the COVID-19 care hospital associated with primary to tertiary care in New Delhi, India. A total of 124 COVID-19 confirmed cases enrolled in two phases (January-March 2021; April-June 2021) who consented for 48hrly saliva and nasopharyngeal swab (NPS) specimens till discharge from the hospital for SARS-CoV-2 detection were included. The specimens obtained were tested for SARS-CoV-2 by Real-Time PCR.Results: The sensitivity and the specificity of RT-PCR on saliva were 81.7 % and 85.0 %, respectively. The sensitivity of saliva-based PCR was comparable in symptomatic and asymptomatic patients (81.6 % vs 82.1 %). The sensitivity of saliva-based PCR markedly increased in the second phase of enrollment as compared to the first phase (92.6 % vs 78.5 %) indicating higher level of salivary shedding by the delta variant of SARS-CoV-2. The sensitivity of PCR on saliva was the highest up to day seven of illness. The median duration of RNA shedding in saliva was comparable among the symptomatic and asymptomatic patients. The severity of the disease was not associated with the duration of SARS-CoV-2 shedding in saliva.Conclusions: SARS-CoV-2 shedding in saliva continued till seven days in large number of patients including asymptomatic patients. Saliva is non-inferior to NPS specimen in the diagnosis of SARS-CoV-2. Saliva specimen is recommended as a good alternate to NPS for SARS-CoV-2 testing.