Clinical performance and potential of a SARS-CoV-2 detection kit without RNA purification steps

Abstract

Objectives Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is rapidly spreading globally. Early diagnosis plays an essential role in controlling the infection. Therefore, early and accurate SARS-CoV-2 detection assays along with easy operation are required. The aim of this study was to compare the clinical performance of the Ampdirect™ 2019-nCoV Detection Kit (SHIMADZU assay), which does not require RNA purification steps, with that of the preexisting SARS-CoV-2 detection assays, which use a purified RNA template. Methods A total of 71 samples (65 nasopharyngeal specimens and 6 sputum specimens) were collected from 32 individuals, including patients infected with SARS-CoV-2 and those with suspected infection. The sensitivity and kappa (κ) coefficient were assessed between the SARS-CoV-2 detection assays using the reference standard, which was defined as a true positive result by any one of the four SARS-CoV-2 detection assays. Results The overall sensitivity and κ coefficient of the SHIMADZU assay were 86.0% (95% confidence interval [CI]: 77.9–94.2) and 0.83 (95% CI: 0.69–0.96), respectively. In particular, among the 18 samples collected within 10 days from symptom onset, the sensitivity and κ coefficient of the SHIMADZU assay were 100% and 1.0, respectively. Conclusions Although a relatively small number of samples was evaluated, the SHIMADZU assay showed good analytical performance and as such would be highly useful for the detection of SARS-CoV-2. The test can be performed easily and quickly and has the potential for future applications in situations where a highly sensitive diagnosis is required.

Viral load may impact the diagnostic performance of nasal swabs in nucleic acid amplification test and quantitative antigen test for SARS-CoV-2 detection

“…Just after the samples were collected, we performed the NAAT and QAT simultaneously using the fresh samples. The NAAT was performed on a LightCycler480 System (Roche Diagnostics K.K., Basel, Switzerland) using the Ampdirect™ 2019-nCoV Detection Kit (Shimadzu Corporation, Kyoto, Japan) [ 7 ]. The QAT was performed on the fully automated Lumipulse L2400 (Fujirebio Inc., Tokyo, Japan) using Lumipulse Presto SARS-CoV-2 Ag (Fujirebio Inc., Tokyo, Japan) [ 8 ].…”

Analysis of diagnostic performance and factors causing nonspecific reactions in SARS-CoV-2 rapid antigen detection tests

“…RT-PCR was performed on a LightCycler480 System (Roche, Basel, Switzerland) using the Ampdirect ™ 2019 Novel Coronavirus Detection Kit (Shimazu Corporation, Kyoto, Japan) [ 9 ]. All assays were performed according to the manufacturer's protocol, and samples were judged as positive or negative based on the cycle threshold (Ct) value.…”

Factors affecting the sensitivity of quantitative severe acute respiratory syndrome coronavirus 2 antigen test

“…The N1 and N2 primer-probe sets of Ampdirect have the same nucleotide sequences as the primer-probe set recommended by the Centers for Disease Control and Prevention [ 7 ]. The detection limits of Ampdirect using artificially synthesized RNA had a sufficient “detection power” of 1000 copies/mL for N1 and 4200 copies/mL for N2 [ 8 ]. A mixture of the sample (5 μL) and treatment solution (5 μL) was pretreated at 90 °C for 5 min and then added to the PCR solution.…”