The predictive value of computed tomography and Haemophilus influenzae capsular antigen in subdural fluid collections.

A study was made of 52 patients with Haemophilus influenzae type B meningitis complicated by subdural collections of fluid to determine which of these collections were sterile (effusions) and which infected (empyema). This differentiation is important for the treatment which differs in the two conditions. Cranial computed tomography (CT) alone was not as reliable as the combination of CT associated with detection of Haemophilus influenzae capsular antigen, in accurately predicting if a subdural fluid collection was infected, or had a high probability of becoming infected.