Is serum procalcitonin a reliable diagnostic marker in children with acute respiratory tract infections? A retrospective analysis

Acute respiratory tract infections (ARI) in children are often treated with antibiotics even without evidence of bacterial infection. Serum procalcitonin (PCT) is elevated in bacterial but not in viral infections. We performed a retrospective analysis of children in the PID-ARI.net study on respiratory infections to address the question of whether plasma PCT could potentially distinguish between bacterial infections requiring antibiotic therapy and viral ARI. We analysed data on 327 children who had been included in the German PID-ARI.net study and in whom nasopharyngeal aspirates had been analysed with a 19-valent multiplex reverse transcription-polymerase chain reaction-enzyme-linked immunosorbent assay for viral and atypical bacterial pathogens. Serum PCT was determined using a quantitative immunoassay (BRAHMS Kryptor PCTsensitive, Henningsdorf, Germany). We then focussed specifically on those children who were treated with antibiotics and therefore had been suspected of having bacterial infection but who had a serum PCT level lower than 0.1 ng/ml. Out of 327 children, 132 had serum PCT levels below 0.1 ng/ml. Of these 132, 38 children had been treated with antibiotics. After exclusion of 26 patients (with critical illnesses, antibiotics on admission or for reasons other than ARI), 12 children remained for further evaluation. Of these 12 children, four had atypical pneumonia; four others had positive virus testing, and, in the last four, the aetiology of ARI remained unknown; evidence of bacterial infection could not be detected in any. Taken the results of this retrospective analysis, serum PCT values below 0.1 ng/ml might be a marker to identify children with acute respiratory tract infection in whom antibiotic treatment could be withheld. However, only a prospective intervention trial will prove the general safety of this limit.