Comparative evaluation of a dual-target real-time RT-PCR assay for COVID-19 diagnosis and assessment of performance in pooled saliva and nasopharyngeal swab samples

Yip, Cyril C. Y.; Leung, Kit-Hang; Ng, Anthony C. K.; Chan, Kwok-Hung; To, Kelvin K. W.; Chan, Jasper F. W; Hung, Ivan F. N.; Cheng, Vincent C. C.; Sridhar, Siddharth

Objectives: Sensitive molecular diagnostic assays are essential for COVID-19 diagnosis. We evaluated the Hecin Scientific SARS-CoV-2 nucleic acid test kit, a dual-target real-time RT-PCR assay targeting the SARS-CoV-2 N and ORF1ab genes. Methods: The Hecin test kit’s diagnostic performance in detecting SARS-CoV-2 RNA was compared to the LightMix Modular SARS and Wuhan CoV E-gene kit (TIB Molbiol) and an in-house single-tube nested real-time RT-PCR using 296 clinical specimens, 11 proficiency testing samples, and 30 low-positive deep throat saliva and nasopharyngeal swab (NPS) samples pooled into negative samples in ratios of 1:5, 1:10, and 1:30. Results: The limit-of-detection of the Hecin test kit was around 500 dC/mL for the N and ORF1ab targets. Sensitivity and specificity of the Hecin test kit were 98.1% (95% CI: 93.4–99.8%) and 100% (98.1–100%), respectively, when measured against the reference method. The Hecin test kit showed fair sensitivity (80%) in low-positive NPS samples pooled in ratios of 1:5 and 1:10. Its performance in pooled samples could be dramatically improved by adjusting the assay Ct cutoff. Conclusion: The Hecin test kit enables sensitive and specific detection of SARS-CoV-2 in clinical samples and pooled samples.