Spit or Swab? The Diagnostic Accuracy of Saliva-Based Testing as a Sars-Cov-2 Surveillance Tool

Keywords: qRT-PCR, rapid antigen test, pooling, SARS-CoV-2, COVID-19

Abstract

Background. Nasopharyngeal swab/oropharyngeal swab (NPS/OPS) qRT-PCR is the gold standard for detecting SARS-CoV-2. However, it has its own limitations including cost and invasiveness. As an alternative, individual qRT-PCR testing of saliva samples was validated and shown to be comparable in sensitivity and specificity with NP-OP qRT-PCR. To further maximize its utility, the researchers wish to explore antigen and pooled testing methods.

Objective. The study aimed to evaluate the diagnostic accuracy of detecting SARS-CoV-2 infection using saliva-based pooled qRT-PCR and rapid antigen test compared with individual saliva qRT-PCR.

Methodology. In this retrospective cross-sectional study, saliva specimen from individuals aged 18 years old and above from the outpatient specimen collection station at the Philippine Children’s Medical Center were tested individually using qRT-PCR (Mag-bind RNA Extraction Kit/MACURA, Allsheng Extraction Machine, Sansure PCR kit, and MA-600 Sansure Biotech). Non-probability convenience sampling was utilized. Based on the individual results, pools of five (5) individual specimens, which includes one (1) positive sample were tested with qRT-PCR for sensitivity. DNK-2150-1S Dynamiker SARS-CoV-2 Ag Rapid Test (Dynamiker Biotechnology Co., Ltd., Tianjin, China) was also used to test individual saliva specimens.

. Out of 196 individual saliva specimens, 73 were detected to have SARS-COV-2 by qRT-PCR, while the remaining 123 were negative. Compared with the individual saliva qRT-PCR, rapid antigen tests done showed sensitivity of 46.58% (95% CI 35.13%, 58.02%), specificity of 86.18% (95% CI 80.08%, 92.28%), positive and negative predictive value of 66.67% (95% CI 53.71%, 79.60%) and 73.10% (95% CI 65.89%, 80.32%) respectively. Based on the results of individual saliva-based qRT-PCR, 62 pools were tested and showed sensitivity of 98.39% (95% CI 91.34%, 99.96%).

Conclusion and Recommendation. Pooled saliva-based testing for SARS-CoV-2 is comparable with individual saliva-based rapid antigen testing. The use of rapid antigen testing is less sensitive and less specific compared with qRT-PCR consistent with prior reports. Additional studies are recommended to determine optimal conditions for testing.

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Author Biographies

Raymundo Lo, Philippine Children’s Medical Center, Quezon City, Philippines

Head, Philippine Children’s Medical Center  COVID-19 Testing Laboratory

Farrah Kristine Santiago, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Specialist III

Grig Misiona, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Specialist III

Melani Sionzon, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Specialist III

Danielle Anne Gonong, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Officer III

Jill Jaime, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Officer III

Jan Roman Ayco, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Officer III

Aquiles Joseph Lira, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Officer III

Erik Francis Rarugal, Philippine Children's Medical Center, Quezon City, Philippines

Medical Technologist I

Jon Carlo Crisostomo, Philippine Children's Medical Center, Quezon City, Philippines

Medical Technologist I

Manuel Bautista Jr., Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Kenneth Chrysostom Ibarra, Philippine Children’s Medical Center

Medical Technologist I

Eunice Jane Ciriaco, Philippine Children's Medical Center, Quezon City, Philippines

Medical Technologist I

Arielle Trish Zamora, Philippine Children's Medical Center, Quezon City, Philippines

Medical Technologist I

Kimberly Abundo, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Emmylou Tarnate, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Jonathan Nario, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Jan Joseph Hernandez, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Kathleen Mae Montes, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist I

Ma. Anabella Recio, Philippine Children’s Medical Center, Quezon City, Philippines

Medical Technologist IV

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Published
2022-11-18
How to Cite
Lo, R., Santiago, F. K., Misiona, G., Sionzon, M., Gonong, D. A., Jaime, J., Ayco, J. R., Lira, A. J., Rarugal, E. F., Crisostomo, J. C., Bautista Jr., M., Ibarra, K. C., Ciriaco, E. J., Zamora, A. T., Abundo, K., Tarnate, E., Nario, J., Hernandez, J. J., Montes, K. M., & Recio, M. A. (2022). Spit or Swab? The Diagnostic Accuracy of Saliva-Based Testing as a Sars-Cov-2 Surveillance Tool . PJP, 7(2). Retrieved from https://philippinejournalofpathology.org/index.php/PJP/article/view/333
Section
Original Articles