Clinical performance of Fujirebio Lumipulse G SARS-CoV-2 rapid antigen test

ABSTRACT

Introduction: SARS-CoV-2 infection has plagued the world for the past two years, during which time it has become necessary to use screening tests to prevent the spread of the virus, especially among high-risk patients. The gold standard for the detection of viral RNA is real-time PCR (RT-PCR). This technique requires special care when handling samples, as well as being time-consuming and costly. To meet the need for mass screening, antigenic tests were developed and continuously improved over the years. In our study, we examined the performance of Lumipulse G SARS-CoV-2 Ag (Fujirebio, Japan), a quantitative and automated chemiluminescence enzymeimmunoassay- based antigen test. Material(s) and Method(s) Our study includes 160 subjects (median age 38 years, interquartile range (IQR) 24-58 years;43% females) screened for SARS-COV-2 at the Service of Laboratory Medicine of Pederzoli Hospital (Peschiera del Garda, Verona, Italy), between August 16 and September 15, 2021. A nasopharyngeal swab was collected for each subject and analyzed at the same time by antigen test Fujirebio Lumipulse G SARS-CoV-2 Ag and by molecular test performed by Altona Diagnostics RealStar SARSCoV- 2 RT-PCR Kit (Altona Diagnostics GmbH, Hamburg, Germany). Result(s) A significant Spearman's correlation was found between values of Fujirebio Lumipulse G SARS-CoV-2 Ag and measurable Ct values of SARSCoV- 2 of both the S (r= -0.94;p<0.001) and E genes (r= -0.95;p<0.001). The sensitivity and specificity at 1.0 pg/ mL (cut-off already used by other authors to discriminate samples positive for SARS-CoV-2) were 0.71 and 1.00. We also used a locally calculated threshold of 0.60 pg/mL (sensitivity 0.88;specificity 0.75). The exclusion of samples tested positive at molecular testing with Ct values comprised between 25-37 enabled the attainment of better diagnostic performance on the 103 residual samples using the 0.60 pg/mL cut-off. Conclusion(s) the results of our study confirm the good performance of Fujirebio Lumipulse G SARS-CoV-2 Ag (considering cutoff 1.0 pg/mL), especially in samples with high viral load (i.e., Ct value <25), which has proved even better using our locally-calculated cut-off (i.e., 0.60 pg/mL).