Laboratory Evaluation of Rapid Antigen Detection Tests for More-Sensitive Detection of Respiratory Syncytial Virus Antigen

We evaluated two currently available rapid antigen detection tests (RADTs) for Respiratory syncytial virus (RSV), Sofia® RSV FIA and BinaxNOW RSV Card (BinaxNOW). Between November 2017 and February 2018, 395 nasopharyngeal swabs were collected from children diagnosed with acute respiratory infections. The swabs were evaluated using the aforementioned RADTs, the reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR), and the direct immunofluorescence assay (DFA). The sensitivity of Sofia® RSV FIA (80.82%) was significantly higher than that of BinaxNOW (53.42%) when RT-qPCR was used as the standard. This was confirmed with DFA. The sensitivities of Sofia® RSV FIA (85.4% [41/48]) and BinaxNOW (58.3% [28/48]) were higher for RSV A than for RSV B (69.6% [16/23] and 43.5% [10/23], respectively). The optimal critical cycle threshold (Ct) values on RT-qPCR that correlated with Sofia® RSV FIA and BinaxNOW were 24 and 22, respectively. The kappa value for Sofia® RSV FIA and RT–qPCR was 0.962 in patients who were two years old or younger, but 0.648 in those who were more than two years old. Thus, Sofia® RSV FIA is more sensitive than BinaxNOW; its results were affected by the RSV viral strain and load. Sofia® RSV FIA is more effective in children who are ≤ 2 years old than in those who are > 2 years old.