Comparison of Xpert Xpress SARS-CoV-2 Assay Compared with Standard M nCoV Real-Time PCR: Prospective Study.

Background: Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can be diagnosed using rapid real-time polymerase chain reaction (PCR), real-time reverse transcription PCR (rRT-PCR), or rapid antigen testing. Among these, rRT-PCR is considered the gold standard assay. The Xpert Xpress SARS-CoV-2 assay is a rapid, real-time PCR test; approved by the Korean Disease Control and Prevention Agency in 2020. Current performance of the Xpert assay (Xpert) with the STANDARD M nCoV Real-Time Detection kit (SD) were determined.

Methods: All samples used by the SD test team were immediately transferred to the Xpert test team within 24 hours. Both tests were conducted between April 2023 and July 2023. Exclusion criteria were studies which show either inconclusive, invalid, or erroneous results. Positive rate, sensitivity, specificity, overall concordance rate, positive concordance rate, discordance rate, false-positive rate, and false-negative rates of the Xpert assay with the STANDARD M nCoV Real-Time Detection kit were determined.

Results: Samples from 347 patients (174 men and 173 women) with a median age of 60 years (range; 6 - 90 years) were included. Positive rate, sensitivity, specificity, overall concordance rate, positive concordance rate, discordance rate, false-positive rate, and false-negative rates of the Xpert assay were 11.2%, 82.1%, 95.0%, 93.9%, 6.6%, 6.1%, 41.0%, and 1.6%, respectively.

Conclusions: COVID-19 results from Xpert should be confirmed through rRT-PCR because of low sensitivity (82.1%) and high false-positive rate (41.0%).