title: Is serum procalcitonin a reliable diagnostic marker in children with acute respiratory tract infections? A retrospective analysis.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, University Medical Center Freiburg, Mathildenstrasse 1, Freiburg 79106, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Schützle
authors.forename: Johannes
authors.initials: J
authors.lastname: Forster
authors.forename: Andrea
authors.initials: A
authors.lastname: Superti-Furga
authors.forename: Reinhard
authors.initials: R
authors.lastname: Berner
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D002648:Child; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D011498:Protein Precursors / Q000097:blood*; D012141:Respiratory Tract Infections / Q000097:blood* / Q000175:diagnosis* / Q000188:drug therapy; D012189:Retrospective Studies; D012720:Severity of Illness Index
chemical_list: D000900:Anti-Bacterial Agents; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide