Comparison of procalcitonin with C-reactive protein, interleukin 6 and interferon-alpha for differentiation of bacterial vs. viral infections

Background. Procalcitonin (PCT) concentration increases in bacterial infect ions but remains low in viral infections and inflammatory diseases. The cha nge is rapid and the molecule is stable, making it a potentially useful mar ker for distinguishing between bacterial and viral infections, Methods, PCT concentration was determined with an immunoluminometric assay on plasma collected at admission in 360 infants and children hospitalized f or bacterial or viral infection. It was compared with C-reactive protein (C RP), interleukin 6 and interferon-alpha measured on the same sample. Results. The mean PCT concentration was 46 mu g/l (median, 17.8) in 46 chil dren with septicemia or bacterial meningitis, PCT concentration was >1 mu g /l in 44 of 46 in this group and in 59 of 78 children with a localized bact erial infection who had a negative blood culture (sensitivity, 83%), PCT co ncentration was >1 mu g/l in 16 of 236 children with a viral infection (spe cificity, 93%). PCT concentration was low in 9 of 10 patients with inflamma tory disease and fever. A CRP value greater than or equal to 20 mg/l was ob served in gl of 236 patients (26%) with viral infection and in 105 of 124 p atients (86%) with bacterial infection. IL-6 was >100 pg/ml in 14% of patie nts infected with virus and in 53% with bacteria. A secretion of interferon -alpha was found in serum in 77% of viral infected patients and in 8.6% of bacterial infected patients, Conclusions. In this study a PCT value of 1 mu g/l or greater had better sp ecificity, sensitivity and predictive value than CRP, interleukin 6 and int erferon-alpha in children for distinguishing between viral and bacterial in fections. PCT values are higher in invasive bacterial infections, but the c utoff value of 1 mu g/l indicates the severity of the disease in localized bacterial infection and helps to decide antibiotic treatment in emergency r oom, PCT may be useful in an emergency room for differentiation of bacteria l vs. viral infections in children and for making decisions about antibioti c treatments.