May 8, 2020

Detection of Low Levels of SARS-CoV-2 RNA from Nasopharyngeal Swabs Using Three Commercial Molecular Assays

Category: Article Summary

Topic: Testing and Treatment

• Lowe et al. compared the testing results of SARS-CoV-2 between three commercial assays for SARS-CoV-2 (Xpert Xpress SARS-CoV-2, cobas, and Lightmix Modular SARS) using 37 nasopharyngeal (NP) swabs with lower levels of SARS-CoV-2 RNA (30 with Ct value between 30-33.9, 22 with Ct ≥34, and 5 negative for SARS-CoV-2). The overall concordance was 86.5% (32/37), including a 100% concordance for samples with moderate viral concentrations (Ct between 30 to –33.9), but a discordance of 22.7% (5/22) amongst samples with lower viral concentrations (Ct ≥34).Testing of SARS-CoV-2 on the three commercial assays was comparable for NP swabs with moderate Ct values, while high Ct values were less concordant.  

Lowe et al. (Apr 28, 2020). Detection of Low Levels of SARS-CoV-2 RNA from Nasopharyngeal Swabs Using Three Commercial Molecular Assays. Journal of Clinical Virology. https://doi.org/10.1016/j.jcv.2020.104387