Serum procalcitonin in pneumococcal pneumonia in children.

Serum procalcitonin (PCT), a marker of bacterial infection, was measured in children with pneumonia to examine whether PCT can be used to screen pneumococcal (PNC) from viral pneumonia. The number of patients was 132; mean age 3.0 yrs, and 64% were males. In all cases, pneumonia was radiologically confirmed, being alveolar in 46 and interstitial in 86 cases. The aetiology of infection was studied by a panel of serological tests for PNC, for five other respiratory bacteria and for seven common respiratory viruses. PNC infection was found in 25, mixed viral-PNC infections in 13 and viral infection in 17 cases. In general, serum PCT was not associated with the type or aetiology of pneumonia. PCT values were >1.0 mg.L(-1) in 40% of PNC cases, as compared to 12-15% in viral or mixed cases, respectively (p<0.05). PCT values were significantly higher in >2 yrs old children than in younger ones. The cut-off limits of 0.5 ng.mL(-1), 1.0 ng.mL(-1) and 2.0 ng.mL(-1) were tested for screening between PNC and viral pneumonia. The highest sensitivity of 55% was found at the 0.5 ng.mL(-1) cut-off level, whereas the highest specificity of 88% was reached at the level of 1.0 ng.mL(-1). The likelihood ratios, however, were far from optimal for both the positive and negative results. Although marginally higher in pneumococcal pneumonia than in viral pneumonia, serum procalcitonin cannot be used to discriminate between these two types of pneumonia.