Validation and verification of the Abbott RealTime SARS-CoV-2 assay analytical and clinical performance.

High-throughput assays for the SARS-CoV-2 virus are critical to increasing test capacity and slowing the spread of COVID-19. Abbott Molecular developed and received emergency use authorization (EUA) to deploy the new RealTime SARS-CoV-2 assay, run on the automated m2000sp/rt system. To evaluate analytical and clinical performance of the RealTime SARS-CoV-2 assay compared to the SARS-CoV-2 CDC-based laboratory developed test (LDT) in clinical use by the University of Washington Clinical Virology Laboratory (UW Virology). RealTime SARS-CoV-2 assay limit of detection (LOD) was evaluated by testing two dilution panels of 60 replicates each. Cross-reactivity was evaluated by testing 24 clinical samples positive for various non‒SARS-CoV-2 respiratory viruses. Clinical performance was evaluated using 30 positive and 30 negative SARS-CoV-2 clinical samples previously tested using the UW Virology SARS-CoV-2 LDT. Exceeding the 100 copies/mL LOD reported in the RealTime SARS-CoV-2 assay EUA product insert, 19 of 20 replicates were detected at 50 copies/mL and 16 of 20 replicates were detected at 25 copies/mL. All clinical samples positive for 24 non‒SARS-CoV-2 respiratory viruses were SARS-CoV-2 negative on the RealTime SARS-CoV-2 assay. The assay had high sensitivity (93%) and specificity (100%) for detecting SARS-CoV-2 in clinical samples. Two positive samples that tested negative with the RealTime SARS-CoV-2 assay had cycle numbers of 35.94 or greater and required dilution prior to testing. One of these samples was also inconclusive on the SARS-CoV-2 LDT. The RealTime SARS-CoV-2 assay is acceptable for clinical use. With the high-throughput, fully automated m2000 system, this assay will accelerate the pace of SARS-CoV-2 testing.

Degli-Angeli E ，Dragavon J ，Huang ML ，Lucic D ，Cloherty G ，Jerome KR ，Greninger AL ，Coombs RW ... -  《-》

Multiplexing primer/probe sets for detection of SARS-CoV-2 by qRT-PCR.

The novel respiratory virus SARS-CoV-2, responsible for over 380,000 COVID-19 related deaths, has caused significant strain on healthcare infrastructure and clinical laboratories globally. The pandemic's initial challenges include broad diagnostic testing, consistent reagent supply lines, and access to laboratory instruments and equipment. In early 2020, primer/probe sets distributed by the CDC utilized the same fluorophore for molecular detection - requiring multiple assays to be run in parallel - consuming valuable and limited resources. Nasopharyngeal swabs submitted to UW Virology for SARS-CoV-2 clinical testing were extracted, amplified by our laboratory developed test (LDT) - a CDC-based quantitative reverse transcriptase PCR reaction - and analyzed for agreement between the multiplexed assay. Laboratory- confirmed respiratory infection samples were included to evaluate assay cross-reaction specificity. Triplexing correctly identified SARS-CoV-2 in 98.4% of confirmed positive or inconclusive patient samples by single-plex LDT (n = 183/186). All 170 SARS-CoV-2 negative samples tested by single-plex LDT were negative by triplexing. Other laboratory-confirmed respiratory infections did not amplify for SARS-CoV-2 in the triplex reaction. Multiplexing two virus-specific gene targets and an extraction control was found to be comparable to running parallel assays independently, while significantly improving assay throughput.

Perchetti GA ，Nalla AK ，Huang ML ，Jerome KR ，Greninger AL ... -  《-》

High-Throughput Transcription-mediated amplification on the Hologic Panther is a highly sensitive method of detection for SARS-CoV-2.

As the demand for laboratory testing for SARS-CoV-2 increases, additional varieties of testing methodologies are being considered. While real time polymerase chain reaction (RT-PCR) has performed as the main method for virus detection, other methods are becoming available, including transcription mediated amplification (TMA). The Hologic Aptima SARS-CoV-2 Assay utilizes TMA as a target amplification mechanism, and it has only recently received Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA). We sought to compare the sensitivity and specificity of the Aptima SARS-CoV-2 Assay to RTPCR as a means of SARS-CoV-2 detection in a diagnostic setting. We performed a limit-of-detection study (LoD) to assess the analytical sensitivity of TMA and RT-PCR. This preceded a comparison of the methods using previously evaluated clinical specimens (nasopharyngeal swabs) using 116 human specimens tested by both methodologies. Specimens included sixty-one (61) specimens found reactive by real-time PCR, fifty-one (51) found non-reactive, and four (4) deemed inconclusive. The Aptima SARS-CoV-2 Assay showed a markedly higher analytical sensitivity than RT-PCR by LoD study. Evaluation of clinical specimens resulted in fewer inconclusive results by the SARS-CoV-2 assay, leading to potentially higher clinical sensitivity. Higher analytical sensitivity may explain TMA's ability to ascertain for the presence of SARS-CoV-2 genome in human specimens deemed inconclusive by real-time PCR. TMA provides an effective, highly sensitive means of detection of SARS-CoV-2 in nasopharyngeal specimens.

Gorzalski AJ ，Tian H ，Laverdure C ，Morzunov S ，Verma SC ，VanHooser S ，Pandori MW ... -  《-》

Comparison of commercial realtime reverse transcription PCR assays for the detection of SARS-CoV-2.

The emergence of a new coronavirus in Wuhan China has triggered a global need for accurate diagnostic assays. Initially, mostly laboratory developed molecular tests were available but shortly thereafter different commercial assays started to appear and are still increasing in number. Although independent performance evaluations are ongoing, available data is still scarce. Here we provide a direct comparison of key performance characteristics of 13 commercial RT-PCR assays. Thirteen RT-PCR assays were selected based on the criteria that they can be used following generic RNA extraction protocols, on common PCR platforms and availability. Using a 10-fold and 2-fold dilution series of a quantified SARS-CoV-2 cell-cultured virus stock, performance was assessed compared to our in house validated assay. Specificity was tested by using RNA extracted from cultured common human coronaviruses. All RT-PCR kits included in this study exhibited PCR efficiencies > 90%, except for the Sentinel Diagnostics B E-gene RUO assay (80%). Analytical sensitivity varied between 3.3 RNA copies to 330 RNA copies. Only one assay cross reacted with another human coronavirus (MERS). This study provides a technical baseline of 13 different commercial PCR assays for SARS-CoV-2 detection that can be used by laboratories interested in purchasing any of these for further full clinical validation.

Iglói Z ，Leven M ，Abdel-Karem Abou-Nouar Z ，Weller B ，Matheeussen V ，Coppens J ，Koopmans M ，Molenkamp R ... -  《-》

Comparison of the Accula SARS-CoV-2 Test with a Laboratory-Developed Assay for Detection of SARS-CoV-2 RNA in Clinical Nasopharyngeal Specimens.

Several point-of-care (POC) molecular tests have received emergency use authorization (EUA) from the Food and Drug Administration (FDA) for the diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The test performance characteristics of the Accula (Mesa Biotech) SARS-CoV-2 POC test need to be evaluated to inform its optimal use. The aim of this study was to assess the test performance of the Accula SARS-CoV-2 test. The performance of the Accula test was assessed by comparing results of 100 nasopharyngeal swab samples previously characterized by the Stanford Health Care EUA laboratory-developed test (SHC-LDT), targeting the envelope (E) gene. Assay concordance was assessed by overall percent agreement, positive percent agreement (PPA), negative percent agreement (NPA), and Cohen's kappa coefficient. Overall percent agreement between the assays was 84.0% (95% confidence interval [CI], 75.3 to 90.6%), PPA was 68.0% (95% CI, 53.3 to 80.5%), and the kappa coefficient was 0.68 (95% CI, 0.54 to 0.82). Sixteen specimens detected by the SHC-LDT were not detected by the Accula test and showed low viral load burden, with a median cycle threshold value of 37.7. NPA was 100% (95% CI, 94.2 to 100%). Compared to the SHC-LDT, the Accula SARS-CoV-2 test showed excellent negative agreement. However, positive agreement was low for samples with low viral load. The false-negative rate of the Accula POC test calls for a more thorough evaluation of POC test performance characteristics in clinical settings and for confirmatory testing in individuals with moderate to high pretest probability of SARS-CoV-2 who test negative on Accula.

Hogan CA ，Garamani N ，Lee AS ，Tung JK ，Sahoo MK ，Huang C ，Stevens B ，Zehnder J ，Pinsky BA ... -  《-》