0521779407-07 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:10
566 Fever of Unknown Origin(CMV, herpes simplex and zoster), fungal infections, nocardia,
mycobacterial infections, Pneumocystis carinii and other oppor-
tunistic infections
■Careful history may reveal important clues to diagnosis: family his-
tory, social history (drug use, sexual exposures), travel, dietary habits
(unpasteurized products, uncooked meats, raw eggs), recreational or
vocational exposures (animals, ticks, chemicals), household pets
Signs & Symptoms
■Etiologies so varied, any organ system potentially could be involved
■Careful and repeated exams crucial to detect transient, subtle find-
ings that may lead to diagnosis such as rash, conjunctivitis, adenopa-
thy
tests
■Routine blood tests (CBC, electrolytes, liver function studies)
■Blood cultures should be done off antibiotics; ask laboratory to hold
for 2 weeks to detect slow-growing, fastidious organisms (HACEK
organisms, Brucella spp) and request special media if considering
legionella, nutritionally deficient streptococci or bartonella
■Cultures of other fluids (urine, sputum, stool, cerebrospinal fluid,
pleural fluid) done if clinically indicated
■Serologic tests done if specific diagnosis considered; “screening”
serologic tests not cost-effective or helpful; a single elevated micro-
biologic titer rarely confirms diagnosis – a 4-fold rise or fall in titer
required to make diagnosis
■Chest radiograph standard; radiographic evaluation of gallbladder,
intestines, sinuses low yield as routine tests, but done if clinically
indicated; CT scan of abdomen, pelvis and chest often done and
helpful – abnormalities require tissue confirmation to make specific
diagnosis; MRI more sensitive than CT for detecting CNS lesions;
ultrasound sensitive for lesions of hepatobiliary system and kidney;
echocardiography if considering endocarditis or myxoma – trans-
esophageal more sensitive than surface echocardiogram; role of
radionuclide scans unclear – plagued by high rate of false-positive
and -negative results and rarely add to findings of CT or MRI
■Abnormalities should be pursued; sample pleural or peritoneal
fluid (infection/malignancy); biopsy rashes (collagen vascular dis-
eases/infection) and enlarged lymph nodes (malignancy/infection);
bone marrow biopsy has low yield (except in HIV disease, where yield
is high for mycobacterial infection), but risk is low and procedure