Prospective evaluation of rapid antigen tests for diagnosis of respiratory syncytial virus and human metapneumovirus infections

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are two important viral pathogens that cause respiratory tract infections in the pediatric population. The rapid detection of these agents allows the prompt isolation and treatment of infected patients. In the present prospective study, we evaluated the performances of four rapid antigen detection assays, including a rapid chromatographic immunoassay (CIA) for RSV (Directigen EZ RSV; Becton Dickinson, Sparks, MD), a direct fluorescent-antibody assay (DFA) for RSV (Bartels; Trinity Biotech, Carlsbad, CA), and two DFAs for hMPV manufactured by Diagnostic Hybrids Inc. (DHI; Athens, OH) and Imagen (Oxoid Ltd., Basingstoke, Hampshire, United Kingdom). The clinical specimens tested comprised 515 nasopharyngeal aspirates submitted to the Clinical Microbiology Laboratory at Hartford Hospital from 1 November 2006 to 21 April 2007. Compared to the results of real-time reverse transcription-PCR (RT-PCR), the CIA had a sensitivity of 79.8% and a specificity of 89.5%. The RSV DFA with Bartels reagents showed a sensitivity of 94.1% and a specificity of 96.8%. For hMPV, the sensitivity and specificity were 62.5% and 99.8%, respectively, for the DHI DFA and 63.2% and 100%, respectively, for the Imagen DFA. The hands-on and test turnaround times for CIA were 10 and 30 to 60 min, respectively, and the hands-on and test turnaround times for the RSV and hMPV DFAs were 30 and 105 min, respectively. We conclude that while the RSV CIA is user-friendly, it lacks sensitivity and specificity, especially during off-peak months. In contrast, the RSV DFA is more sensitive and specific, but interpretation of its results is subjective and it demands technical time and expertise. Similarly, both hMPV DFAs are highly specific in comparison to the results of RT-PCR, but their sensitivities await further improvements.