Fever of Unknown Origin (FUO) Diagnostic Algorithm STEP 1 Perform a comprehensive history and complete physical examination. STEP 2 PDCs identified? Apply appropriate invasive or noninvasive diagnostic studies for investigation STEP 3 Order CBC, CMP, ESR, CRP, ferritin, TSH, RF, ANA, HIV-1/2 serology, hepatitis A, B, and E, urinalysis with microscopy, tuberculosis skin test or TB whole-blood interferon-γ releasing assay, blood cultures × 3, venous duplex imaging of the lower extremities, CT of chest and abdomen/pelvis, and echocardiography (TTE/TEE). STEP 4 Any positive first-tier testing? STEP 5 Any PDCs by repeat history and physical examination? STEP 6 Order 18FDG-PET/CT scan imaging (if not already performed). STEP 7 If there are still no new PDCs then re-evaluate the patient history and physical examination periodically. Continue to monitor any new PDCs and apply appropriate noninvasive and/or invasive diagnostic testing based upon any new findings. At this stage, empiric use of nonsteroidal anti-inflammatory agents or immunosuppressant therapy such as corticosteroids could be entertained after discussing risks and benefits with the patient. https://academic.oup.com/ofid/artic #Fever #Unknown #Origin #FUO #Diagnosis #Algorithm #infectiousdiseases
