WHAT'S KNOWN ON THIS SUBJECT: Quantitative real-time polymerase chain reaction allows sensitive detection of respiratory viruses. The clinical significance of detection of specific viruses is not fully understood, however, and several viruses have been detected in the respiratory tract of asymptomatic children. WHAT THIS STUDY ADDS:Our results indicate that quantitative real-time polymerase chain reaction is limited at distinguishing acute infection from detection in asymptomatic children for rhinovirus, bocavirus, adenovirus, enterovirus, and coronavirus. abstract BACKGROUND: Acute respiratory illness (ARI) accounts for a large proportion of all visits to pediatric health facilities. Quantitative real-time polymerase chain reaction (qPCR) analyses allow sensitive detection of viral nucleic acids, but it is not clear to what extent specific viruses contribute to disease because many viruses have been detected in asymptomatic children. Better understanding of how to interpret viral findings is important to reduce unnecessary use of antibiotics. OBJECTIVE:To compare viral qPCR findings from children with ARI versus asymptomatic control subjects.METHODS: Nasopharyngeal aspirates were collected from children aged #5 years with ARI and from individually matched, asymptomatic, population-based control subjects during a noninfluenza season. Samples were analyzed by using qPCR for 16 viruses. RESULTS:Respiratory viruses were detected in 72.3% of the case patients (n 5 151) and 35.4% of the control subjects (n 5 74) (P 5 .001). Rhinovirus was the most common finding in both case patients and control subjects (47.9% and 21.5%, respectively), with a population-attributable proportion of 0.39 (95% confidence interval: 0.01 to 0.62). Metapneumovirus, parainfluenza viruses, and respiratory syncytial virus were highly overrepresented in case patients. Bocavirus was associated with ARI even after adjustment for coinfections with other viruses and was associated with severe disease. Enterovirus and coronavirus were equally common in case patients and control subjects.CONCLUSIONS: qPCR detection of respiratory syncytial virus, metapneumovirus, or parainfluenza viruses in children with ARI is likely to be causative of disease; detection of several other respiratory viruses must be interpreted with caution due to high detection rates in asymptomatic children. Although acute respiratory illness (ARI) in childrenaccountsfora large part ofall visits to pediatric health facilities and is a great economic burden on society, 1,2 our tools to diagnose the etiologic agents have until recently been limited. 3 Treatment with antibiotics induces development of antibiotic resistance in bacteria 4 and has a negligible effect on most ARIs, which generally are of viral origin. 5,6 Nevertheless, antibiotics are frequently prescribed due to lack of clinically valid diagnostic tests verifying a viral etiology. 7 Sensitive methods, such as quantitative real-time polymerase chain reaction (qPCR) analyses on nasopharyngeal samples, for a number of viru...

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Acute respiratory tract infections are caused by a large number of viruses. Diagnostic methods have until recently been available only for a limited number of these viruses. With the objective to achieve sensitive assays for all respiratory viruses, a rational workflow in the laboratory, and a short turn-around time, a real-time PCR diagnostic platform for daily rapid detection of 15 respiratory viruses was developed. The system was evaluated on 585 stored nasopharyngeal aspirates from hospitalized children. Previous analysis by immunofluorescence and virus isolation identified viruses in 37% of the samples while the new PCR diagnostic panel detected 57% virus positive samples. The new platform was introduced in the laboratory in October 2007 and has then fully replaced the standard immunofluorescence assay for rapid detection of viruses and virus isolation.