Serum alpha-interferon in lower respiratory tract infections of children

Background. Serum alpha-interferon (IFN-alpha) concentrations are high in some children with viral meningitis and other viral infections. We have tried to assess the utility of determining serum IFN-alpha concentrations as a marker of acute viral. respiratory infections. Methods. Measurement of IFN-alpha via a biologic assay on Madin-Darby bovine kidney cells was performed in 138 patients with lower respiratory tract infection in whom a pathogen was identified. Results. Serum IFN alpha was detectable at the early stage of respiratory infections in the era of 59 of 75 (78.7%) of patients with a viral infection and in 4 of 63 (6.3%) of those with bacterial infection (P < 0.001). In the 4 patients with positive IFN-alpha and bacterial infection, a concomitant viral infection was found. The production of IFN-alpha is independent of age, and detectable levels are found in young infants, including the first 3 months of life, and in children with am acute viral disease. Conclusion. This test could be useful in distinguishing between bacterial and viral origins in lower respiratory tract infection (the specificity was 94% and the sensitivity was 79%) and could help guide the use of antibiotics, but more rapid techniques, available in a matter of hours, are required.