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Table 5 Initial investigations in classical fever of unknown origin

From: Undifferentiated epithelioid sarcoma presenting as a fever of unknown origin: a case report

Diagnostic test Potential diagnostic utility
Initial investigations
 CBC with differential and smear - Neutropenia to determine breadth of possible infection, cytopenias suggesting bone marrow involvement
 Renal function - Glomerulonephritis
 Liver enzymes and LFTs - Hepatic or cholestatic etiologies
 ESR and CRP - Markers signifying an inflammatory process
 Thyroid function - Thyrotoxicosis
 HIV antibody - HIV and potential for opportunistic infections
 Blood cultures - Bacteremia or fungemia
 Urine analysis and microscopy - UTI, glomerulonephritis, or vasculitis
 CXR - Pneumonia, miliary TB, sarcoidosis, or malignancy
Investigations based on diagnostic clues from initial workup
 Echocardiography - Potential endocarditis
 CT - Abscesses, other infections, or malignancy
 Indium-111-WBC scan - To localize any sites of inflammation
 FDG-PET/CT - Careful localization of infection, malignancy, vasculitis, or sarcoidosis
 Lymph node biopsy - Malignancy or infection
 Liver biopsy - Malignancy, infection, or autoimmune diseases
 Bone marrow biopsy - Hematologic malignancy
 Temporal artery biopsy - Giant cell arteritis
  1. CBC complete blood count, CRP C-reactive protein, CT computed tomography, CXR chest X-ray, ESR erythrocyte sedimentation rate, FDG fluorine-18-fluorodeoxyglucose, HIV human immunodeficiency virus, LFT liver function test, PET positron emission tomography, TB tuberculosis, UTI urinary tract infection, WBC white blood cell