Assessment of the clinical and analytical performance of the Aptima SARS-CoV-2 assay using the VALCOR protocol.

BACKGROUND: The COVID-19 pandemic highlighted the importance of diagnostic testing against curbing the spread of SARS-CoV-2. The urgent need and scale for diagnostic tools resulted in manufacturers of SARS-CoV-2 assays receiving emergency authorization that lacked robust analytical or clinical evaluation. As it is highly likely that testing for SARS-CoV-2 will continue to play a central role in public health, the performance characteristics of assays should be evaluated to ensure reliable diagnostic outcomes are achieved. METHODS: VALCOR or "VALidation of SARS-CORona Virus-2 assays" is a study protocol designed to set up a framework for test validation of SARS-CoV-2 virus assays. Using clinical samples collated from VALCOR, the performance of Aptima SARS-CoV-2 assay was assessed against a standard comparator assay. Diagnostic test parameters such as sensitivity, specificity and overall per cent agreement were calculated for the clinical performance of Aptima SARS-CoV-2 assay. RESULTS: A total of 180 clinical samples were tested with an addition of 40 diluted clinical specimens to determine the limit of detection. When compared to the standard comparator assay Aptima had a sensitivity of 100.0% [95% CI 95.9-100.0] and specificity of 96.7% [95% CI 90.8-99.3]. The overall percent agreement was 98.3% with an excellent Cohen's coefficient of κ = 0.967 [95% CI 0.929-1.000]. For the limit of detection, Aptima was able to detect all of the diluted clinical samples. CONCLUSION: In conclusion. validation of Aptima SARS-CoV-2 assay using clinical samples collated through the VALCOR protocol showed excellent test performance. Additionally, Aptima demonstrated high analytical sensitivity by detecting all diluted clinical samples corresponding to a low limit of detection.

Performance Evaluation of the BD SARS-CoV-2 Reagents for the BD MAX System.

Nucleic acid amplification testing (NAAT) for SARS-CoV-2 is the standard approach for confirming COVID-19 cases. This study compared results between two emergency use authorization (EUA) NAATs, with two additional EUA NAATs utilized for discrepant testing. The limits of detection (LOD) for the BD SARS-CoV-2 reagents for the BD MAX system (MAX SARS-CoV-2 assay), the bioMérieux BioFire respiratory panel 2.1 (BioFire SARS-CoV-2 assay), the Roche cobas SARS-CoV-2 assay (cobas SARS-CoV-2 assay), and the Hologic Aptima SARS-CoV-2 assay Panther (Aptima SARS-CoV-2 assay) NAAT systems were determined using a total of 84 contrived nasopharyngeal specimens with 7 target levels for each comparator. The positive and negative percent agreement (PPA and NPA, respectively) of the MAX SARS-CoV-2 assay, compared to the Aptima SARS-CoV-2 assay, was evaluated in a postmarket clinical study utilizing 708 nasopharyngeal specimens collected from suspected COVID-19 cases. Discordant testing was achieved using the cobas and BioFire SARS-CoV-2 NAATs. In this study, the measured LOD for the MAX SARS-CoV-2 assay (251 copies/ml; 95% confidence interval [CI], 186 to 427) was comparable to the cobas SARS-CoV-2 assay (298 copies/ml; 95% CI, 225 to 509) and the BioFire SARS-CoV-2 assay (302 copies/ml; 95% CI, 219 to 565); the Aptima SARS-CoV-2 assay had an LOD of 612 copies/ml (95% CI, 474 to 918). The MAX SARS-CoV-2 assay had a PPA of 100% (95% CI, 97.3% to 100.0%) and an NPA of 96.7% (95% CI, 94.9% to 97.9%) compared to the Aptima SARS-CoV-2 assay. The clinical performance of the MAX SARS-CoV-2 assay agreed with another sensitive EUA assay.

Evaluation of the analytical performance and specificity of a SARS-CoV-2 transcription-mediated amplification assay.

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic requires fast and accurate high-throughput diagnostic tools. To evaluate the analytical performance of the Hologic Aptima transcription-mediated amplification (TMA) assay for detection of SARS-CoV-2 RNA from respiratory samples we analysed 103 clinical and proficiency panel samples pre-tested by real-time RT-PCR (Altona, RealStar) and found a positive percent agreement (sensitivity) of 95.7 % and a negative percent agreement (specificity) of 100 %. The limit of detection of the Aptima test was 150 copies/mL determined as 95 % detection probability. To further assess the Aptima assay's specificity we prospectively analysed 7545 clinical specimens from the upper and lower respiratory tract sent for the purpose of routine SARS-CoV-2 screening. SARS-CoV-2 RNA was detected in 16/7545 (0.2 %) samples by the TMA assay and confirmed independently by the Xpert SARS-CoV-2 RT-PCR (Cepheid); in one case a previous discrepant result was confirmed as true SARS-CoV-2 infection in a subsequent sample from the same patient. Results from the Aptima SARS-CoV-2 TMA assay agreed well with RT-PCR and showed an excellent specificity in a large number of routine specimens despite the low prevalence at that time of the pandemic, indicating that this assay can be used even for screening purposes.

Performance Characteristics of a High-Throughput Automated Transcription-Mediated Amplification Test for SARS-CoV-2 Detection.

The COVID-19 pandemic caused by the new SARS-CoV-2 coronavirus has imposed severe challenges on laboratories in their effort to achieve sufficient diagnostic testing capability for identifying infected individuals. In this study, we report the analytical and clinical performance characteristics of a new, high-throughput, fully automated nucleic acid amplification test system for the detection of SARS-CoV-2. The assay utilizes target capture, transcription-mediated amplification, and acridinium ester-labeled probe chemistry on the automated Panther system to directly amplify and detect two separate target sequences in the open reading frame 1ab (ORF1ab) region of the SARS-CoV-2 RNA genome. The probit 95% limit of detection of the assay was determined to be 0.004 50% tissue culture infective dose (TCID50)/ml using inactivated virus and 25 copies/ml (c/ml) using synthetic in vitro transcript RNA targets. Analytical sensitivity (100% detection) was confirmed to be 83 to 194 c/ml using three commercially available SARS-CoV-2 nucleic acid controls. No cross-reactivity or interference was observed with testing of six related human coronaviruses, as well as 24 other viral, fungal, and bacterial pathogens, at high titers. Clinical nasopharyngeal swab specimen testing (n = 140) showed 100%, 98.7%, and 99.3% positive, negative, and overall agreement, respectively, with a validated reverse transcription-PCR nucleic acid amplification test (NAAT) for SARS-CoV-2 RNA. These results provide validation evidence for a sensitive and specific method for pandemic-scale automated molecular diagnostic testing for SARS-CoV-2.

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

BACKGROUND: 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). OBJECTIVES: 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. STUDY DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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.