A-276 Clinical Performance Evaluation of SMARTCHEK® SARS-CoV-2 Detection Kit and SMARTCHEK® SARS-CoV-2 Fast Detection Kit for Detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Saliva
Authors: Park S , Yoo J , Cho S 
Published: September 2023

Abstract

Background
Saliva is a good alternative to the nasopharyngeal swab because it is non-invasive and does not require separate collection personnel. SMARTCHEK® SARS-CoV-2 Detection Kit (Genesystem, Daejeon, Korea) and SMARTCHEK® SARS-CoV-2 Fast Detection Kit (Genesystem) are rapid PCR kits for SARS-CoV-2 using a microfluidic chip-based PCR method. These two kits can provide results in 40 min and 20 min, respectively, enabling rapid point-of-care diagnostics. This study compared the diagnostic performance of SMARTCHEK® SARS-CoV-2 Detection Kit and SMARTCHEK® SARS-CoV-2 Fast Detection Kit using UF-340 Four-in-One Real-time PCR System (Genesystem) to the STANDARD M nCoV Real-Time Detection kit (SD Biosensor, Korea) using CFX96 Dx System (Bio-Rad Laboratories, Inc., USA) in saliva.

Methods
Saliva was collected in a sterile urine specimen cup after obtaining consent from subjects who were scheduled to perform a COVID-19 PCR within 24 h or had already performed it within 24 h at Ajou University hospital. RNA was extracted by SLA-E13200 (Taiwan Advanced Nanotech Inc., Taoyuan, Taiwan) and Saliva:DirectTM Extraction Buffer (Genesystem), respectively. The Saliva:DirectTM Extraction Buffer was able to extract RNA within 10 min without additional equipment. Real-time PCR was performed according to each manufacturer’s guidelines. The STANDARD M nCoV Real-Time Detection kit after RNA extraction by SLA-E13200 was tested as the control method. The positive, negative, and overall concordance rates were calculated for evaluation of correlation with the control method. This study was approved by Ajou University Hospital IRB.

Results
Among 66 samples, the control method identified 50 negative (76%) and 16 positive (24%) samples, two of which showed Ct values exceeding 30 (13% of positive samples). When RNA was extracted with SLA-E13200, the positive, negative, and overall concordance rates of SMARTCHEK® SARS-CoV-2 Detection Kit and SMARTCHEK® SARS-CoV-2 Fast Detection Kit were 100%, 100%, 100%, and 94%, 100%, 98%, respectively. A positive sample with a Ct value exceeding 30 showed discrepant results with SMARTCHEK® SARS-CoV-2 Fast Detection Kit. After RNA extraction with Saliva:DirectTM Extraction Buffer, positive condordance rates of STANDARD M nCoV Real-Time Detection Kit, SMARTCHEK®SARS-CoV-2 Detection Kit, and SMARTCHEK® SARS-CoV-2 Fast Detection Kit compared to the control method were 67%, 75%, and 81%, respectively. All negative concordance rates were 100%, and overall concordance rates were 94%, 94%, 95%, respectively. Four out of 16 positive samples by the control method showed inconclusive results with the STANDARD M nCoV Real-Time Detection Kit when RNA was extracted with Saliva:DirectTM Extraction Buffer.

Conclusion
SMARTCHEK® SARS-CoV-2 Detection Kit and SMARTCHEK® SARS-CoV-2 Fast Detection Kit can quickly and accurately diagnose COVID-19 in saliva after RNA extraction with SLA-E13200, and may be useful especially in small to medium-sized laboratories or areas lacking in space or equipment. Although the RNA extraction process with the Saliva:DirectTM Extraction Buffer is fast, simple, and doesn’t require supplementary equipment, some improvement is warranted before use in clinical settings due to relatively low positive concordance rates.