Fever Without Focus Labs

Aka: Fever Without Focus Labs

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II. Precautions

  1. Labs do not triage initial management of infants under 1 month or ill appearing children under 36 months
    1. All labs are performed in Fever Without Focus if under 1 month or ill appearing and under 36 months
    2. All infants with these risks are admitted and started on empiric antibiotics
    3. Leukocytosis has poor Test Sensitivity of serious Bacterial Infection <60 days
      1. Cruz (2017) JAMA Pediatr 171(11):172927 [PubMed]
  2. Blood Cultures
    1. Obtain in all febrile newborns age <30 days
    2. Avoid Blood Cultures in non-toxic febrile children without localizing symptoms >3 months of age
      1. Blood Cultures are more likely to be contaminated than true infection (RR 100x)

III. Labs: Age under 60 days

  1. See Fever Without Focus Management Birth to 3 Months
  2. CBC with differential
    1. Positive inflammatory marker if Absolute Neutrophil Count (ANC) >4000 cells/mm3
  3. Procalcitonin (PCT)
    1. Positive inflammatory marker if >0.5 ng/ml
    2. When Procalcitonin is unavailable or pending, fever > 101.3 F (38.5 C) may be used as inflammatory marker
  4. C-Reactive Protein (CRP)
    1. Positive inflammatory marker if >20 mg/L
  5. Blood Culture (one set)
  6. Urinalysis with microscopic exam
    1. Positive if any Leukocyte esterase present OR Urine White Blood Cells (WBC) >10 cells/mm3
  7. Urine Culture
    1. Send in all febrile infants <=21 days or if positive Urinalysis
  8. Lumbar Puncture
    1. Indications
      1. All ill appearing infants <60 days
      2. All febrile infants age <21 days old
      3. Febrile infants age 21 to 28 days old
      4. Optional in febrile infants age 29 to 60 days
    2. Positive criteria
      1. Any Neutrophils (PMNs) seen on grams stain OR
      2. White Blood Cells >18 cells in age <28 days (or >9 cells in age 29 to 60 days)
  9. Basic Metabolic Panel
    1. Indicated in age <21 days
  10. Total Serum Bilirubin
    1. Indicated in age <21 days
  11. Respiratory infection labs as indicated for respiratory symptoms (or at time of outbreak)
    1. Chest XRay
    2. Influenza Swab
    3. Covid19 nasal swab
    4. Respiratory Syncytial Virus (RSV) nasal swab
  12. Herpes Simplex Virus (HSV)
    1. Indications
      1. HSV symptoms within 1 week of delivery
      2. Household HSV contact
      3. Vesicles
      4. Seizure
      5. Hypothermia
      6. Ill appearing infant
      7. Sepsis-like syndrome
    2. HSV Labs
      1. CSF Herpes Simplex Virus PCR
      2. Herpes Simplex Virus PCR and culture swabs from eye, Rectum (and Vesicle if present)

IV. Labs: Age 2 to 36 months AND signs of serious illness

  1. Complete Blood Count (CBC) with differential
  2. Blood Culture
  3. Urinalysis and Urine Culture
    1. Age less than 24 months: Obtain both Urinalysis and Urine Culture
    2. Age 24 to 36 months: Consider Urinalysis and Urine Culture if urinary tract source is suspected
  4. Lumbar Puncture for CSF Studies and culture
    1. Age 1 to 3 months: All ill appearing infants
    2. Age 3-36 months: Neurologic or meningeal signs present
  5. Chest XRay Indications
    1. Respiratory symptoms
    2. Rectal Temperature > 102º F
    3. WBC >20,000
  6. Stool Culture and Fecal Leukocytes Indications
    1. Diarrheal illness

V. Labs: Age 2 to 36 months without signs of serious illness

  1. Consider Influenza test during Influenza season in ages 3 to 36 months
    1. Positive Influenza test often obviates need for further Fever Without Focus evaluation
  2. Complete Blood Count (CBC) with differential
  3. Blood Culture (draw and hold) when other labs obtained
  4. Urinalysis and Urine Culture
    1. Age less than 24 months: Obtain both Urinalysis and Urine Culture
    2. Age 24 to 36 months: Consider Urinalysis and Urine Culture if urinary tract source is suspected
  5. Lumbar Puncture for CSF Studies and culture
    1. Age <1 month: All febrile infants
    2. Age 1 to 3 months Indications
      1. All ill, toxic appearing infants
      2. Absolute Neutrophil Count >10,000/mm3
      3. CRP >20 ng/ml or Procalcitonin >0.5 ng/ml
      4. Mintegi (2017) Arch Dis Child 102(3): 244-9 [PubMed]
    3. Age 3-36 months Indications
      1. Altered Level of Consciousness or Neurologic signs
      2. Meningeal signs present
    4. Precaution
      1. Younger infants are less likely to demonstrate meningeal signs (Exercise caution)
      2. Normal WBC Count (between 5000 to 15000) does not rule-out Meningitis
        1. Bonsu (2003) Ann Emerg Med 41:206-14 [PubMed]
    5. Interpretation: Findings Suggestive of Bacterial Meningitis in Age <3 months
      1. CSF WBC >20/mm3
      2. CSF Protein >100 mg/dl
      3. CSF Glucose <20 ng/dl
      4. Leazer (2017) Pediatrics 139(5):e20163268 [PubMed]
  6. Chest XRay Indications
    1. May avoid Chest XRay in Wheezing consistent with Asthma or Bronchiolitis
    2. Respiratory symptoms (respiratory distress, Tachypnea, pulmonary rales)
    3. Rectal Temperature > 102.2º F
    4. White Blood Cell Count >20,000
    5. Oxygen Saturation <95% (Hypoxia)
  7. Stool Culture and Fecal Leukocytes Indications
    1. Diarrheal illness

VI. Labs: Urinalysis and Urine Culture

  1. Indications
    1. Perform in all Fever Without Focus children age <24 months
      1. UTI is among the top two causes of serious Bacterial Infection under 36 months
        1. Rudinsky (2009) Acad Emerg Med 16(7): 585-90 [PubMed]
      2. Serious Urinary Tract Infections (Pyelonephritis, urosepsis) are increasing in Incidence
        1. Copp (2011) J Urol 186(3): 1028-34 [PubMed]
    2. Age <5 years AND 3 of the following criteria
      1. Pain or crying with urination
      2. Foul smelling urine
      3. Prior Urinary Tract Infection
      4. Severe Illness signs
      5. Absence of severe cough
      6. Ebell (2018) Am Fam Physician 97(4): 273-4 [PubMed]
  2. Clean catch, catheterized urine or suprapubic aspirate for all samples
    1. Bag urine has 85% False Positive Rate
    2. Bag urine may be used as reassuring if negative, but positive (LE, nitrite, pyuria) requires confirmation
    3. Fineell (2011) Pediatrics 128(3):e749-70 [PubMed]
  3. Urine Culture all samples
    1. Urine dipstick False Negative Rate: 12%
    2. Gorelick (1999) Pediatrics 104(5): e54 [PubMed]
  4. Findings suggestive of Urinary Tract Infection
    1. Pyruia (>5 WBCs per HPF or >10 WBCs on enhanced Urinalysis)
    2. Urine Culture >50,000 CFU on urine catheterization or suprapubic sample
  5. Febrile UTI follow-up
    1. Age <2 years requires renal and Bladder Ultrasound (and if abnormal, VCUG)

VII. Labs: Infectious markers (age under 3 months)

  1. Inflammatory markers with greater Positive Predictive Value of serious infection than White Blood Cell Count
    1. C-Reactive Protein (CRP)
      1. CRP <10 mg/L has a Negative Predictive Value for Sepsis of 99%
      2. CRP >40 mg/L is more suggestive of serious Bacterial illness (but not sensitive or specific)
      3. Single CRP is inadequate for reassurance (repeat in 24 hours)
      4. NSAIDs modify CRP significantly (Ibuprofen increases, Naproxen decreases)
      5. Bilavsky (2009) Acta Paediatr 98(11): 1776-80 +PMID:19664100 [PubMed]
      6. McWilliam (2010) Arch Dis Child Educ Pract Ed 95(2): 55-8 +PMID:20351152 [PubMed]
    2. Procalcitonin (PCT)
      1. Procalcitonin rapidly increases above normal threshold with fever onset in serious Bacterial Infection
      2. PCT <0.5 ng/ml has a Negative Predictive Value for serious Bacterial Infection of 90%
      3. PCT >0.6 (and WBC >19k, blasts >1.8k, Neutrophils >13k) suggests serious Bacterial Infection
      4. Olaciregui (2009) Arch Dis Child 94(7): 501-5 +PMID:19158133 [PubMed]
      5. Mahajan (2014) Acad Emerg Med 21(2): 171-9 +PMID:24673673 [PubMed]
    3. Laboratory Score combines CRP, Procalcitonin and Urine Dipstick
      1. See Laboratory Score for Febrile Infants
      2. Score >3 points suggests higher risk for serious Bacterial Infection
    4. References
      1. Freyne (2013) Clin Pediatr 52(6): 503-6 +PMID:23613177 [PubMed]
      2. Stein (2015) Clin Pediatr 54(5): 439-44 +PMID:25294884 [PubMed]
  2. Rapid urine pneumococcal Antigen assay
    1. Currently being researched for clinical application
    2. Test Sensitivity in pneumococcal bacteremia: 96%
    3. High False Positive Rate
    4. Neuman (2003) Pediatrics 112:1279-82 [PubMed]

VIII. References

  1. Herman (2015) Crit Dec Emerg Med 29(12):14-19
  2. (1993) Ann Emerg Med 22(3):628-37 [PubMed]
  3. Baraff (2000) Ann Emerg Med 36:602-14 [PubMed]
  4. Baraff (1993) Pediatrics 92(1): 1-12 [PubMed]
  5. Cioffredi (2016) JAMA Pediatr 170(8):794-800 [PubMed]
  6. Daaleman (1996) Am Fam Physician 54(8):2503 [PubMed]
  7. Hamilton (2013) Am Fam Physician 87(4): 254-60 [PubMed]
  8. Hamilton (2020) Am Fam Physician 101(12): 721-9 [PubMed]
  9. Kimmel (1996) Fam Pract Recert 18(7):69-85 [PubMed]
  10. Luszczak (2001) Am Fam Physician 64(7):1219-26 [PubMed]
  11. Lopez (1997) Postgrad Med 101(2):241-52 [PubMed]
  12. Sur (2007) Am Fam Physician 75:1805-11 [PubMed]

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