Apart from laboratory work up investigations like<unk>  and<unk>   may be helpful in finding cause of FUO provided the diagnostic clues are present which makes these investigation essential.
Fever of unknown origin echocardiography and ultrasound
Fever of unknown origin physical examination
Fever of unknown origin other diagnostic studies
Fever of unknown origin CT scan
Fever of unknown origin other imaging findings
Fever of unknown origin MRI
Fever of unknown origin surgery
ST elevation myocardial infarction chest x ray