Procalcitonin in children admitted to hospital with community acquired pneumonia

Aims-To assess the sensitivity, specificity, and predictive value of procal citonin (PCT) in differentiating bacterial and viral causes of pneumonia. Methods-A total of 72 children with community acquired pneumonia were studi ed. Ten had positive blood culture for Streptococcus pneumoniae and 15 had bacterial pneumonia according to sputum analysis (S pneumoniae in 15, Haemo philus influenzae b in one). Ten patients had Mycoplasma pneumoniae infecti on and 37 were infected with viruses, eight of whom had viral infection plu s bacterial coinfection. PCT concentration was compared to C reactive prote in (CRP) concentration and leucocyte count, and, if samples were available, interleukin 6 (IL-6) concentration. Results-PCT concentration was greater than 2 mug/l in all 10 patients with blood culture positive for S pneumoniae; in eight of these, CRP concentrati on was above 60 mg/l. PCT concentration was greater than 1 mug/l in 86% of patients with bacterial infection (including Mycoplasma and bacterial super infection of viral pneumonia). A CRP concentration of 20 mg/l had a similar sensitivity but a much lower specificity than PCT (40% v 86%) for discrimi nating between bacterial and viral causes of pneumonia. PCT concentration w as significantly higher in cases of bacterial pneumonia with positive blood culture whereas CRP concentration was not. Specificity and sensitivity wer e lower for leucocyte count and IL-6 concentration. Conclusions-PCT concentration, with a threshold of 1 mug/l is more sensitiv e and specific and has greater positive and negative predictive values than CRP, IL-6, or white blood cell, count for differentiating bacterial and vi ral causes of community pneumonia in untreated children admitted to hospita l as emergency cases.