From the Guidelines
For pediatric patients with prolonged fever, the initial laboratory tests should include a complete blood count (CBC) with differential, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), blood cultures, urinalysis with culture, and a comprehensive metabolic panel, as these tests help identify infections, inflammatory conditions, and organ dysfunction 1.
Key Laboratory Tests
- Complete blood count (CBC) with differential to assess for signs of infection or inflammation
- C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to evaluate the level of inflammation
- Blood cultures to identify bacteremia or sepsis
- Urinalysis with culture to diagnose urinary tract infections, which are a common cause of fever in pediatric patients 1
- Comprehensive metabolic panel to assess organ function and identify any electrolyte imbalances
Additional Targeted Tests
- Chest X-ray to evaluate for pneumonia or other respiratory infections
- Tuberculin skin test to diagnose tuberculosis
- Serology for specific infections, such as Epstein-Barr virus, cytomegalovirus, or typhoid fever
- Imaging studies, such as ultrasound or CT scan, may be necessary in some cases to evaluate for underlying conditions like abscesses or malignancies
Approach to Evaluation
The approach to evaluating pediatric patients with prolonged fever should be stepwise, starting with non-invasive tests and progressing based on clinical findings and initial results 1. This systematic evaluation helps identify the underlying cause of the fever, which could range from common infections to less common conditions like juvenile idiopathic arthritis, inflammatory bowel disease, malignancies, or immunodeficiencies. In cases where the fever persists beyond 2-3 weeks, more specialized tests may be necessary, including bone marrow examination, autoimmune markers like ANA and rheumatoid factor, or even tissue biopsy 1.
From the Research
Laboratory Tests for Prolonged Fever in Pediatrics
The following laboratory tests are used to evaluate prolonged fever in pediatric patients:
- White blood cell count 2
- Blood smear 2
- Hemoglobin level 2
- Erythrocyte sedimentation rate (ESR) 2, 3
- C-reactive protein (CRP) 2, 3, 4, 5
- Platelet count 3
- Biochemical examinations of serum 3
- Urinalysis 3, 4, 5
- Chest X-ray 3, 4, 5
- Analysis of cerebrospinal fluid (CSF) 3
- Echocardiography 3
Significance of Laboratory Tests
These laboratory tests help in identifying the underlying cause of prolonged fever in pediatric patients. For example:
- CRP concentration is a valuable laboratory test in the evaluation of febrile young children who are at risk for occult bacteremia and serious bacterial infection 4
- A CRP cutoff point of 7 can maximize both sensitivity and specificity in diagnosing serious bacterial infection 4
- Rapid CRP test can reduce the number and cost of laboratory examinations, and save time for patients and practitioners 5
Diagnostic Approach
The diagnostic approach for prolonged fever in pediatric patients involves:
- Assessing the duration and magnitude of fever 2
- Evaluating the patient's age, sex, and growth curves 2
- Conducting basic laboratory investigations 2
- Considering the patient's medical history and physical examination findings 2, 3
- Using laboratory tests to guide further evaluation and management 2, 3, 4, 5