Can respiratory syncytial virus etiology be diagnosed clinically? A hospital-based case-control study in children under two years of age.

An unmatched, hospital-based case-control study was performed, to determine, whether respiratory syncytial virus (RSV) etiology in hospitalized young children can be predicted clinically. Children under 2 years of age admitted with a lower respiratory tract infection in three hospitals in northern Germany were included (one tertiary and two secondary centers). Cases were children tested positive for RSV by multiplex RT-PCR. One control group consisted of children tested negative for RSV in the multiplex-RT-PCR and a second control group consisted of patients in whom no PCR was done. A weighted backward stepwise logistic regression model was applied for multivariate analysis. RSV-etiology could be predicted with a sensitivity of 72.8% and a specificity of 73.2%. Young age, disease entity--pneumonia or bronchiolitis, center, intercostal retractions, absence of an underlying condition, low level of C-reactive protein, short duration of symptoms (all on admission), prematurity and epidemiologic year were predictive; anatomical infiltrates and wheezing were not. Pathogen specific diagnosis is necessary for individual therapy, allocation in observational studies or treatment trials and for surveillance of airway infections in children, since the positive predictive value is too low for an accurate diagnosis and decision making. Multivariate techniques are effective tools in complex clinical research for deconfounding.