From the Guidelines
For a patient presenting with fever, asthenia, and myalgia, the initial workup should include a thorough history and physical examination to identify potential causes, as recommended by 1.
Recommendations
- Complete Blood Count (CBC) with differential to evaluate for signs of infection or inflammation, as suggested by 1
- Blood cultures to identify potential bacterial causes, as recommended by 1
- Electrolyte panel and renal function tests to assess for any electrolyte imbalances or renal involvement, as suggested by 1
- Liver function tests to evaluate for hepatitis or other liver conditions, as recommended by 1
- Influenza testing during flu season, as suggested by 1
- Consider testing for other viral infections such as COVID-19, mononucleosis, or HIV, depending on the patient's risk factors and exposure history
- Imaging studies such as chest X-ray or CT scans may be indicated based on the patient's symptoms and physical examination findings, as recommended by 1
Empiric Antibiotic Therapy
Empiric antibiotic therapy may be considered if bacterial infection is suspected, with choices such as ceftriaxone 1g IV every 24 hours or azithromycin 500mg PO daily, depending on the suspected source and severity of infection, as suggested by 1. Antipyretics such as acetaminophen 650mg PO every 4-6 hours or ibuprofen 400mg PO every 6 hours can be used to manage fever and body aches.
It is crucial to tailor the workup and treatment to the individual patient based on their specific presentation, medical history, and risk factors, as recommended by 1. Consultation with infectious disease specialists may be necessary for complex or unclear cases.
From the Research
Initial Evaluation
The workup for a patient presenting with fever, asthenia, and myalgia should begin with a comprehensive history and physical examination to help narrow potential etiologies 2. This initial evaluation is crucial in identifying localizing signs and symptoms that can guide further testing.
Differential Diagnosis
The differential diagnosis for fever of unknown origin is broad and can be categorized into four subgroups: infections, malignancies, autoimmune conditions, and miscellaneous 3. In patients with common variable immune deficiency, the differential diagnosis can also include infectious, autoimmune, or malignancy-related etiologies 4.
Diagnostic Testing
Initial testing should include an evaluation for infectious etiologies, malignancies, inflammatory diseases, and miscellaneous causes such as venous thromboembolism and thyroiditis 2. The following tests may be useful:
- Erythrocyte sedimentation rate or C-reactive protein levels to assess for inflammation
- 18F fluorodeoxyglucose positron emission tomography scan, with computed tomography, if initial evaluation is unrevealing and inflammation is present
- Tissue biopsy, such as liver, lymph node, temporal artery, skin, skin-muscle, or bone marrow biopsy, if noninvasive diagnostic tests are unrevealing
Special Considerations
In immunocompromised patients, the differential diagnosis and workup may need to be tailored to their specific condition 5. For example, patients with HIV/AIDS may require additional testing for opportunistic infections. Similarly, patients with common variable immune deficiency may require testing for infectious and autoimmune etiologies 4.
Key Points to Consider
- A thorough history, physical examination, and standard laboratory testing remain the basis of the initial evaluation of the patient with fever of unknown origin 3
- Empiric antimicrobial therapy should be avoided except in patients who are neutropenic, immunocompromised, or critically ill 2
- The workup should be guided by the patient's clinical presentation, medical history, and laboratory results 2, 4, 5, 3, 6