Serum C-reactive protein cannot differentiate bacterial and viral aetiology of community-acquired pneumonia in children in primary healthcare settings

Whether serum C-reactive protein (CRP) can be used to distinguish bacterial from viral pneumonia was studied in 193 paediatric patients who were ident ified in a prospective, population-based study. The proportion of patients < 5 y of age was 51%, 53% of these and 12% of the older patients were treat ed in hospital. Pneumococcal aetiology of infection was studied in paired s era by antibody and immune-complex assays, and chlamydial, mycoplasmal and viral aetiologies by routine antibody assays. CRP concentration was measure d by immunoturbidometry. Pneumococcal infection (mixed infections with othe r agents included) was present in 57 cases, mycoplasmal and/or chlamydial i nfection (pneumococcal infections excluded) in 43, and viral infection (pne umococcal, mycoplasmal and chlamydial infections excluded) in 29 cases, The mean CRP concentrations (95% confidence interval) in these groups were 26. 8 mg/l (20.1-33.5 mg/l), 31.8 mg/l (20.5-33.1 mg/l) and 26.1 mg/l (19.1-33. 1 mg/l), respectively, and 24.9 mg/l (18.8-31.0 mg/l) in patients with no a etiological findings. When CRP values were compared between the 2 diagnosti c groups of pneumococcal infections (antibody and immune-complex positive) no difference was found. In infants < 12 months of age the mean CRF concent ration was 14.6 mg/l, and in 11 (65%) of them it was unmeasurable (<10 mg/l ), No significant differences were seen between hospitalized patients and o utpatients, In conclusion, CRP concentration had no significant association with the microbial aetiology of pneumonia.