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A decision tree based on procalcitonin and C-reactive protein levels as a potential diagnostic tool to distinguish PFAPA flares from acute bacterial and viral infections

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Periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA) is a disease of unknown etiology and unclear pathophysiology. Considering the inexistence of specific laboratory test for PFAPA, it remains a diagnosis of exclusion.


We searched for practical use of procalcitonin (PCT) and C-reactive protein (CRP) in differentiating PFAPA attacks from acute bacterial and viral infections.


Levels of PCT and CRP were measured in 35 PFAPA patients during 67 PFAPA febrile episodes and in 86 children diagnosed with acute bacterial (n=47) or viral (n=39) infection. We used the C4.5 algorithm (statistical classifier) to construct a decision tree.


Statistical analysis with the use of C4.5 algorithm resulted in the following decision tree: viral infection if CRP≤19.1 mg/L; otherwise for cases with CRP>19.1 mg/L: PFAPA if PCT≤0.65 ng/mL, bacterial infection if PCT>0.65ng/mL. The rule was effective in 83.7% of the cases. Febrile episodes during PFAPA flares, bacterial and viral infections were classified with the sensitivity of 76.1%, 93.6% and 84.6% and specificity of 89.5%, 88.7% and 96.5% respectively.


Differences in PCT and CRP levels during PFAPA attacks, bacterial and viral diseases may be used to build a simple decision tree. When interpreted cautiously and with reference to the clinical context, it might present a potential diagnostic tool for distinguishing PFAPA flares from acute infections.

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Correspondence to B Kraszewska-Glomba.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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  • Viral Infection
  • Decision Tree
  • Statistical Classifier
  • Stomatitis
  • Unknown Etiology