White blood cells, C-reactive protein and erythrocyte sedimentation rate in pneumococcal pneumonia in children.

We evaluated the applicability of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood cell count (WBC), and absolute neutrophil count (ANC), in the screening of pneumococcal (PNC) pneumonia in children. In 1981-1982, 161 children were treated for radiologically verified community-acquired pneumonia in the hospital during a period of 12 months. The Streptococcus pneumoniae aetiology of infection was studied by antigen, antibody and immune complex assays in acute and convalescent sera. In acute blood samples, CRP was measured by the immunonephelometric method, ESR by the Westergren method, WBC using an automatic cell counter, and thereafter the ANC was calculated after microscopic examination of peripheral smears. CRP and ESR were significantly higher in patients with alveolar (n=53) than in those with interstitial (n=108) pneumonia. CRP, ESR and ANC were significantly higher in PNC (n=29) than in viral (n=23) pneumonia. The values in mixed PNC and viral infections (n=17) were approximately midway between PNC and viral cases. All cases with serologic evidence of S. pneumoniae aetiology were combined (n=46) for calculation of diagnostic parameters. When a cut-off limit of 60 mg x L(-1) was used, CRP had a sensitivity of 26% and a specificity of 83% in the screening of PNC pneumonia. We conclude that C-reactive protein and erythrocyte sedimentation rate have a limited capacity to differentiate between pneumococcal and nonpneumococcal pneumonia. C-reactive protein is recommended as the first-line method of screening, and the value of 60 mg x L(-1) as the cut-off limit.