Serum procalcitonin, C-reactive protein and interleukin-6 for distinguishing bacterial and viral pneumonia in children

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Abstract
Serum procalcitonin (PCT), C-reactive protein (CRP) and interleukin-6 (IL-6) concentrations were measured in 126 children hospitalized for community-acquired, radiologically confirmed pneumonia to assess whether these host response values could be used to distinguish bacterial from viral pneumonia. The samples for PCT, CRP and IL-6 measurements were obtained on admission or the first day of hospitalization. The etiology of pneumonia was studied with an extensive panel of methods that detected 6 bacteria and 11 viruses. In all, 54% had evidence of bacterial pneumonia, and 32% had evidence of sole viral pneumonia. In 14% of the cases the etiology could not be determined. Children with bacterial pneumonia had significantly higher PCT (median 2.09 ng/ml vs. 0.56 ng/ml, P = 0.019) and CRP concentrations (96 mg/l vs. 54 mg/l, P = 0.008) than those with sole viral etiology. However, the values markedly overlapped. No significant difference in IL-6 concentrations was seen between the two patient groups. Using PCT ≥ 2.0 ng/ml, CRP ≥ 150 mg/l or IL-6 ≥ 40 pg/ml, the specificity was ≥80% for bacterial pneumonia. The sensitivities with these cutoff values were 50% for PCT, 31% for CRP and 34% for IL-6. The results indicate that the measurement of serum PCT, CRP and IL-6 has little value in the differentiation of bacterial and viral pneumonia in children. However, in some patients with very high serum PCT, CRP or IL-6 values, bacterial pneumonia is probable.