Evaluation of symptomatic patient saliva as a sample type for the Abbott ID NOW COVID-19 assay

SoRelle, J.; Mahimmainathan, L.; McCormick-Baw, C.; Cavuoti, D.; Lee, F.; Bararia, A.; Thomas, A.; Sarode, R.; Clark, A. E.; Muthukumar, A.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has presented significant challenges for laboratories including supply chain limitations with restricted access to reagents and sample collection materials (i.e. swabs, viral transport media (VTM)) for patients testing. Therefore, saliva has been evaluated as an alternative specimen for COVID-19 diagnosis. comparable performance between dry nasal swabs (NS) and nasopharyngeal swabs (NPS) collected in VTM has been observed with the ID NOW for SARS-CoV-2; the majority of false-negative results occur with higher cycle number (CN) or cycle threshold (Ct) values suggesting low viral load in these specimens. We performed clinical validation of saliva specimens on the ID NOW molecular platform to detect SARS-CoV-2. Saliva was compared to nasopharyngeal swabs tested on the ID NOW and the Cepheid molecular assay. We also performed stability studies of saliva samples over 5 days. A total of 96 saliva samples and 64 paired NPS were analyzed. We observed 78% (18/23) positive percent agreement (PPA) and 100% (44/44) negative percent agreement (NPA) between matched saliva and nasopharyngeal specimens performed on ID NOW. We found 83% (19/23) PPA and 100% NPA (25/25) between saliva run on the ID NOW and Cepheid assay. Six saliva specimens positive for SARS-CoV-2 were continuously positive for five days when stored at room temperature. Therefore, we propose further investigation of saliva as an alternative sample type for testing symptomatic patients with ID NOW as a promising method to address COVID-19 testing.