Negative Results of Nucleic Acid Amplification Tests for SARS-CoV-2 in Clinical Practice May Vary among Six Molecular Assays in Patients with COVID-19.

Several commercial nucleic acid amplification tests (NAATs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed. We used 6 kits available in Japan in 13 NAAT-positive specimens with crossing point values >36 and 7 NAAT-negative specimens from patients with coronavirus disease 2019 (COVID-19), and their results were compared. Specimens positive in ≥2 assays were considered true-positive and examined for concordance with the specimen results. The SARS-CoV-2 Detection Kit -Multi- (Toyobo M; Toyobo, Osaka, Japan) using extracted RNA had the highest concordance (κ = 1.00). This was followed by Cobas® SARS-CoV-2 (Roche, Basel, Switzerland) (κ = 0.79). There was a weak correlation between the number of negative results for each kit and the number of days between onset and testing (Spearman rank correlation: ρ = 0.44; P < 0.05). We believe that the variations in results among kits for specimens with low viral loads should not be problematic when these kits are used for screening infectious patients because these variations are more likely to be observed in specimens tested many days after onset (i.e., those that have lost their infectivity). However, it may be better to use a test for suspected late-stage COVID-19 with a low viral load, such as Toyobo M or Cobas.

Evaluation of the QIAstat-Dx Respiratory SARS-CoV-2 panel, a rapid multiplex PCR method for the diagnosis of COVID-19.

INTRODUCTION: Rapid, simple, and accurate methods are required to diagnose coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study aimed to evaluate the performance of the QIAstat-Dx Respiratory SARS-CoV-2 Panel (QIAstat-SARS-CoV-2), a rapid multiplex PCR assay for SARS-CoV-2 detection. METHODS: Nasopharyngeal swabs (NPS) that were obtained from patients with COVID-19 who were diagnosed at the National Center for Global Health and Medicine were used in this study. When the NPS samples were found to be negative for SARS-CoV-2 after treatment, they were used as negative samples. We evaluated the performance of the QIAstat-SARS-CoV-2 comparing SARS-CoV-2 detection with the National Institute of Infectious Diseases in Japan-recommended real-time polymerase chain reaction (RT-PCR) method (NIID-RT-PCR). RESULTS: In total, 45 NPS samples were analyzed. The proportion of overall agreement between QIAstat-SARS-CoV-2 and NIID-RT-PCR on 45 samples was 91.0% with a sensitivity of 84.0% (21/25), specificity at 100% (20/20), negative predictive value at 83.3% (20/24), and positive predictive value at 100% (21/21). There were no patients with co-infections with pathogens other than SARS-CoV-2. CONCLUSIONS: QIAstat-SARS-CoV-2 showed a high agreement in comparison with the NIID-RT-PCR for the detection of SARS-CoV-2. The QIAstat-SARS-CoV-2 also provided a rapid and accurate diagnosis for COVID-19, even when the concurrent detection of other respiratory pathogens was desired, and therefore, has the potential to direct appropriate therapy and infection control precautions.