Performance of a rapid antigen test (Binax NOW® RSV) for diagnosis of respiratory syncytial virus compared with real-time polymerase chain reaction in a pediatric population

BackgroundInfants from Alaska's Yukon–Kuskokwim Delta (YKD) have a high respiratory syncytial virus (RSV) hospitalization rate (104/1000/yr). Appropriate patient management requires rapid and accurate RSV diagnosis. Antigen-based methods are often used in clinical settings, but these tests can lack sensitivity.ObjectiveWe compared Binax NOW® RSV (BN) used for RSV diagnosis in the YKD hospital with a real-time polymerase chain reaction assay (RT-qPCR) used for viral surveillance.Study designBetween October 2005 and September 2007 we obtained nasopharyngeal washes (NPW) from children <3 years hospitalized with a lower respiratory tract infection. The NPW were tested using BN and RT-qPCR.Results79/311 (25%) children had RSV infection as determined by RT-qPCR. As compared with RT-qPCR, sensitivity and specificity of BN were 72% and 97%, respectively. The sensitivity of BN was higher in children <1 year compared with children ≥1 year (79% vs. 52%; p = 0.025), children with bronchiolitis compared with children without bronchiolitis (89% vs. 38%; p < 0.001), and children with a shorter duration of symptoms before testing (0–1 (92%) vs. 2–4 (78%) vs. 5+ (65%) days; p = 0.04). The median RSV viral load in NPW positive by BN and RT-qPCR was 1.01 × 109 copies/mL vs. a median of 5.25 × 107 copies/mL for NPW positive by RT-qPCR only (p < 0.001).ConclusionRT-qPCR is more sensitive than BN in detecting RSV infection. BN sensitivity is high in children with bronchiolitis, but the sensitivity is low when children present with a non-bronchiolitis illness, especially after a longer duration of symptoms before testing.