C-REACTIVE PROTEIN IN VIRAL AND BACTERIAL RESPIRATORY-INFECTION IN CHILDREN

C-reactive protein (CRP) was studied in 209 children treated in hospit al due to middle or lower respiratory tract infection with serological ly demonstrated viral or bacterial aetiology. Of the 110 patients with serological evidence of bacterial infection, either alone or in assoc iation with viral infection, 52% had CRP > 20 mg/l, 35% > 40 mg/l and 15% > 80 mg/l. Of the 99 patients with serological evidence of viral i nfection alone, 35% had CRP > 20 mg/l, but only 12% > 40 mg/l and 5% > 80 mg/l. Nearly all, 88%, of the 25 patients with CRP > 40 mg/l in as sociation with viral infection had either an infectious focus, specifi c microbial or non specific laboratory evidence suggestive of bacteria l infection. By calculating diagnostic parameters at 3 cut-off levels of CRP, the level 40 mg/l seemed more useful than 20 mg/l or 80 mg/l f or differentiation between viral and bacterial infections. By using a CRP value of 40 mg/l as a screening limit sensitivity was 0.55, specif icity 0.88, positive predictive value 0.76, negative predictive value 0.55, and likelihood ratios of a positive and negative test result 2.9 and 0.74, respectively. It is conluded that low CRP values do not rul e out bacterial aetiology of respiratory infection in children. On the other hand viral infection without bacterial involvement is very impr obable if CRP is > 40 mg/l. Our results suggest that high CRP values r ule out viral infection as a sole aetiology of infection; bacterial in fection and antibiotic treatment should be considered in these cases.