title: Discrepancies between plasma procalcitonin and C-reactive protein levels are common in acute illness.
abstract: OBJECTIVE
  Procalcitonin (PCT) and C-reactive protein (CRP) are biomarkers of bacterial infection with distinct clinical qualities. This study aimed to determine the occurrence and significance of discrepancies in plasma PCT and CRP levels in hospitalised children.
  
  
  METHODS
  This was a single centre, retrospective analysis of simultaneous PCT and CRP measurements. Clinical characteristics, microbiological findings and diagnoses were compared between cases in which only PCT or CRP levels were elevated.
  
  
  RESULTS
  We studied 635 pairs of PCT and CRP measurements and found discrepancies in 29% of these. In the group with increased PCT and low CRP, there were more children with hypoxia or haemodynamic stress (14 versus 0, p < 0.001) and more bacteraemic patients (eight versus zero, p = 0.001) than in the group with low PCT and increased CRP. The latter group was associated with focal bacterial infections (three versus 18, p = 0.009), inflammatory conditions (one versus 12, p = 0.016) and postoperative setting (one versus 19, p = 0.001). Diabetic ketoacidosis was associated with a marked elevation of PCT.
  
  
  CONCLUSIONS
  Discrepancies in plasma PCT and CRP levels occurred in 29% of acutely ill children. Both biomarkers can increase in the absence of bacterial infection, but PCT may offer an advantage over CRP in the diagnosis of bacteraemia.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Lauri
authors.identifier: http://orcid.org/0000-0001-8935-5032
authors.initials: L
authors.lastname: Ivaska
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Varpu
authors.initials: V
authors.lastname: Elenius
authors.affiliation: Tykslab, Turku University Hospital, Turku, Finland.|Joint Clinical Biochemistry of University of Turku, Turku, Finland.
authors.forename: Ilkka
authors.initials: I
authors.lastname: Mononen
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Ruuskanen
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Ville
authors.initials: V
authors.lastname: Peltola
mesh_terms: D000208:Acute Disease; D016470:Bacteremia / Q000097:blood / Q000175:diagnosis; D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D016883:Diabetic Ketoacidosis / Q000097:blood / Q000175:diagnosis*; D006760:Hospitalization; D006801:Humans; D007223:Infant; D016015:Logistic Models; D012189:Retrospective Studies; D014777:Virus Diseases / Q000097:blood / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; D002116:Calcitonin; D002097:C-Reactive Protein
keywords: Bacteraemia; C-reactive protein; Ketoacidosis; Procalcitonin; Serious bacterial infection