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Fever Without Apparent Source in Children Aged 3-36 Months

General Information


  • acute febrile illness with no obvious source of fever after thorough history and physical exam1,2,3,4
  • fever commonly defined as rectal temperature ≥ 38 degrees C (100.4 degrees F) documented in clinical setting or at home within past 24 hours1,2,3,4

Also called

  • fever without source
  • fever without localizing signs
  • fever without focus
  • unexplained fever


General references used

  1. National Institute for Health and Care Excellence. Feverish illness in children: assessment and initial management in children younger than 5 years. NICE 2017 Aug:CG160PDF
  2. American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Pediatric Fever; Mace SE, Gemme SR, Valente JH, et al. Clinical Policy for Well-Appearing Infants and Children Younger Than 2 Years of Age Presenting to the Emergency Department With Fever. Ann Emerg Med. 2016 May;67(5):625-639.e13
  3. Wing R, Dor MR, McQuilkin PA. Fever in the pediatric patient. Emerg Med Clin North Am. 2013 Nov;31(4):1073-96
  4. Ishimine P. Risk stratification and management of the febrile young child. Emerg Med Clin North Am. 2013 Aug;31(3):601-26

Recommendation grading systems used

  • American College of Emergency Physicians (ACEP) grading system for recommendations
    • levels of recommendation
      • Level A - generally accepted principles for patient management that reflect high degree of clinical certainty, based on Class I studies or overwhelming evidence from Class II studies
      • Level B - recommendations for patient management that may identify particular strategy or range of management strategies that reflect moderate clinical certainty, based on Class II studies or strong consensus of Class III studies
      • Level C - other strategies for patient management based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus (in absence of any published literature)
    • strength of evidence
      • Class I - interventional studies including clinical trials, observational studies including prospective cohort studies, aggregate studies including meta-analyses of randomized clinical trials only
      • Class II - observational studies including retrospective cohort studies, case-controlled studies, aggregate studies including meta-analyses that directly address the issue
      • Class III - descriptive cross-sectional studies, observational reports including case series and case reports, or consensus studies including published panel consensus by acknowledged groups of experts
    • Reference - ACEP clinical policy on fever in children younger than three years presenting to emergency department with fever (14520324Ann Emerg Med 2003 Oct;42(4):530)
  • American Academy of Pediatrics (AAP) guideline grading system
    • grades of recommendation
      • Strong recommendation if both
        • preponderance of benefit or harm
        • evidence quality A, B, or X
      • Recommendation if both
        • preponderance of benefit or harm
        • evidence quality B, C, or X
      • Option if either
        • preponderance of benefit or harm with evidence quality D
        • balance of benefit and harm with evidence quality A, B, or C
      • No Recommendation if both
        • balance of evidence and harm
        • evidence quality D
    • levels of evidence quality
      • Evidence Quality A - well-designed randomized controlled trials or diagnostic studies on relevant population
      • Evidence Quality B - randomized controlled trials with minor limitations; overwhelmingly consistent evidence from observational studies
      • Evidence Quality C - observational studies (case-control and cohort design)
      • Evidence Quality D - expert opinion, case reports, reasoning from first principles
      • Evidence Quality X - exceptional situations where validating studies cannot be performed and there is a clear preponderance of benefit or harm
    • Reference - AAP clinical practice guideline on diagnosis and management of initial urinary tract infection (UTI) in febrile infants and children aged 2-24 months (21873693Pediatrics 2011 Sep;128(3):595)
  • Pediatric Infectious Diseases Society/Infectious Diseases Society of America (PIDS/IDSA) grades of recommendation
    • strength of recommendation
      • Strong recommendation - desirable effects clearly outweigh undesirable effects, or vice versa
      • Weak recommendation
        • if high-quality or moderate-quality evidence - desirable effects closely balanced with undesirable effects
        • if low-quality evidence - uncertainty in estimates of desirable effects, harms, and burden; desirable effects, harms, and burden may be closely balanced
        • very low-quality evidence - major uncertainty in estimates of desirable effects, harms, and burden; desirable effects, harms, and burden may be closely balanced
    • quality of evidence
      • High-quality evidence - consistent evidence from well-performed randomized controlled trials (RCTs) or exceptionally strong evidence from unbiased observational studies
      • Moderate-quality evidence - evidence from RCTs with important limitations (inconsistent results, methodologic flaws, indirect, or imprecise) or exceptionally strong evidence from unbiased observational studies
      • Low-quality evidence - evidence for ≥ 1 critical outcome from observational studies, RCTs with serious flaws or indirect evidence
      • Very low-quality evidence - evidence for ≥ 1 critical outcome from unsystematic clinical observations or very indirect evidence
    • Reference - PIDS/IDSA clinical practice guideline on management of community-acquired pneumonia in infants and children > 3 months old (21880587Clin Infect Dis 2011 Oct;53(7):e25), commentary can be found in 22423129Clin Infect Dis 2012 Jun;54(12):1816

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How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T115836, Fever Without Apparent Source in Children Aged 3-36 Months; [updated 2018 Nov 30, cited place cited date here]. Available from Registration and login required.

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