Table 3. Thorough evaluation of possible etiologies of fever.
1Cytomegalovirus 2Epstein-Barr virus 3Transthoracic echocardiogram 4Antinuclear antibody 5Anti-double-stranded DNA antibody 6Rheumatoid factor 7Hemophagocytic lymphohistiocytosis 8Ultrasound
CMV: Cytomegalovirus; EBV: Epstein-Barr virus; IgG: Immunoglobulin G; IgM: Immunoglobulin M; TTE: Transthoracic echocardiogram; ANA: Antinuclear antibody; Anti-dsDNA antibody: Anti-double-stranded DNA antibody; RF: Rheumatoid factor; HLH: Hemophagocytic lymphohistiocytosis.
| Category | Evaluation | Result |
| Bacterial | Blood cultures, urinalysis, urine Legionella antigen, cat scratch disease testing | Negative |
| Viral | CMV¹, EBV², respiratory viral panel | Negative |
| Fungal | Cryptococcal antigen, Fungitell, galactomannan, Histoplasma urine antigen | Negative |
| Parasitic | Toxoplasma antibodies, IgG and IgM | Negative |
| Tick-borne illness | Lyme titer, Babesia PCR, Ehrlichia testing, Anaplasma testing | Negative |
| Endocarditis | Blood cultures, TTE³ | Negative |
| Malignancy | CT of the chest, abdomen, and pelvis | Negative |
| Autoimmune | ANA⁴, anti-dsDNA antibody⁵, RF⁶ | Negative |
| Hyperinflammatory | Still's disease and HLH⁷ evaluation | Negative |
| Advanced pathogen testing | Karius testing | Negative |
| Clot | US⁸ of the lower extremities | Negative |
| Medication | Medication review | Negative |