Evaluation of four methods for the diagnosis of respiratory syncytial virus infection in older adults

OBJECTIVE: To evaluate four methods of rapid diagnosis of respiratory syncytial virus (RSV) infection in older adults and to compare sensitivities with serologic analysis. DESIGN: Prospective comparative analysis. SETTING: Two adult daycenters. PATIENTS: Frail older persons attending the daycenter who developed signs or symptoms of acute respiratory illness between the months of December and February. MEASUREMENTS: Viral cultures performed by standard technique and bedside inoculation: antigen detection by indirect immunofluorescence assay (IFA) and Directigen enzyme immunoassay (EIA) on nasal brush samples; serologic analysis of acute and convalescent sera using EIA. RESULTS: RSV infection was documented by serology in 11 of 54 (20%) subjects during the study period. Bedside viral cultures were the most sensitive assay and were positive in 6/9 infections. Standard viral culture detected 5/11 cases. Both methods of rapid antigen detection were found to be insensitive, with 1/11 detected by IFA and 0/11 detected by EIA. CONCLUSION: Rapid antigen tests for the diagnosis of RSV in older persons should be used with caution.