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.