Value of antigen quantitation in Haemophilus influenzae type b meningitis

We studied Haemophilus influenzae type b meningitis in 68 patients to evaluate whether quantitative determination of PRP in body fluids obtained at admission or measurement of the duration of its presence helped identify patients at risk for complications. Geometric mean admission PRP concentrations in CSF, blood, and urine increased with severity of disease, but individual values varied greatly. Measurements of the duration of antigenemia and antigenuria also varied widely and were best predicted by the admission or peak PRP concentration. The mean duration of both antigenemia and antigenuria increased with severity of disease. In contrast, the elimination half-life of PRP did not differ significantly with severity of hospital course, peak PRP concentration in blood or urine, or patient age. Clearance from CSF could not be accurately assessed, but PRP was detectable in only six of 41 patients in whom spinal fluid was obtained after the eighth day of hospitalization; all had complicated courses. Although latex particle agglutination assay is a valuable aid in rapid diagnosis of invasive Hib infections, the predictive value of antigen quantitation at admission and the determination of its duration in body fluids is limited by the wide range of observed values.