Aetiology of respiratory tract infections: clinical assessment versus serological tests.

Two hundred and fifty ambulatory patients with febrile respiratory tract infections were included in a prospective study, aimed at determining the reliability of physicians judgements relating to the aetiology of the infection. Compared with advanced serological testing, physicians' judgements for a bacterial/atypical, rather than viral, aetiology had a negative predictive value of 60% and a positive predictive value of only 50%. We conclude that physicians' ability to assess whether the infectious aetiology of RTI is viral or bacterial/atypical is low and no more reliable than tossing a coin.