Despite the wide variety of exotic diseases, the most common infections among series of FUOs have not changed over the past half century. These continue to include typhoid fever, tuberculosis, amebic abscesses, and malaria. Fever of unknown origin is more often caused by an atypical presentation of a common entity than by a rare disorder. [1}
Initial laboratory testing in all patients [1]
- Culture blood x3, ESR, TB interferon gamma release assay, HIV
- CT chest and abdomen
- Mycobacterial blood culture
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) – Measurement of the ESR seems to have its greatest use in establishing a serious underlying cause of FUO. In a review of 263 patients with FUO who had ESR elevations above 100 mm/hour, 58 percent had malignancy (most commonly lymphoma, myeloma, or metastatic colon or breast cancer) and 25 percent had infection (eg, endocarditis) or systemic rheumatic diseases (eg, rheumatoid arthritis or giant cell arteritis). However, other causes of FUO, such as drug hypersensitivity reactions, thrombophlebitis, and renal disease, particularly nephrotic syndrome, may be associated with a very high ESR in the absence of infection or malignancy. A normal ESR or CRP also suggests that a significant inflammatory process, of whatever origin, is absent; however, there are exceptions. As an example, some patients with giant cell arteritis have a normal ESR.
- Serum lactate dehydrogenase
- Tuberculin skin test or interferon-gamma release assay
- HIV immunoassay and HIV viral load for patients at high risk
- Three routine blood cultures drawn from different sites over a period of at least several hours without administering antibiotics, if not already performed
- Rheumatoid factor
- Creatine phosphokinase
- Heterophile antibody test in children and young adults
- Antinuclear antibodies
- Serum protein electrophoresis
- Computed tomography (CT) scan of the chest and abdomen.
- Procalcitonin, a serum biomarker that is elevated with certain bacterial infections, has no clear role in distinguishing between bacterial infections and other causes of FUO, and we do not recommend checking it as part of the FUO evaluation
No pharmaceutical treatment is available.