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.

BACKGROUND: Infants 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. OBJECTIVE: We 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 DESIGN: Between 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. RESULTS: 79/311 (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 × 10(9)copies/mL vs. a median of 5.25 × 10(7)copies/mL for NPW positive by RT-qPCR only (p<0.001). CONCLUSION: RT-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.