Detecting respiratory viruses in asymptomatic children.

BACKGROUND Viral respiratory infections are among the most common reasons for hospitalization of children in the United States. Our objective was to compare molecular and conventional methods in a cohort of hospitalized children with and without symptoms of respiratory viral illness (RVI). METHODS We conducted a retrospective cohort study of infants and toddlers hospitalized between December 2007 and March 2008 at Johns Hopkins Hospital. Five hundred sixty-nine of 641 patient visits (89%) were tested on admission. Conventional tests (immunochromatography, direct fluorescent antibody, shell vial and tube culture) were performed on all patients and nucleic acid tests (NATs) were performed on available samples (n = 306). Viruses were grouped into those routinely (group 1) and those not routinely (group 2) detected by conventional methods. RESULTS In children with RVI symptoms (n = 148), NATs identified a virus in 83% of specimens compared with 49% by conventional methods (P < 0.001), but detected a similar percentage of specimens with group 1 viruses (48.6% and 55.4%; P = 0.13) compared with conventional tests. In children without RVI symptoms (n = 158), NATs identified a virus in 41.7% of specimens compared with 4.4% by conventional tests (P < 0.001) and identified more group 1 viruses (9.5% and 4.4%; P = 0.03) compared with conventional tests. Group 2 viruses were identified by NATs in a similar percentage of symptomatic and asymptomatic patients (25% and 32.3%; P = 0.20). CONCLUSIONS Molecular assays may have several advantages over conventional methods for detecting respiratory viruses, including improved sensitivity and rapid detection, but given the high prevalence of positive results in children without RVI symptoms, results should be interpreted cautiously.