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 an 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.