Elsevier

Seminars in Nuclear Medicine

Volume 43, Issue 5, September 2013, Pages 333-339
Seminars in Nuclear Medicine

FDG-PET in Fever of Unknown Origin

https://doi.org/10.1053/j.semnuclmed.2013.04.005Get rights and content

Fever of unknown origin (FUO) is commonly defined as fever higher than 38.3°C on several occasions during at least 3 weeks with uncertain diagnosis after a number of obligatory tests. FUO remains a clinical challenge as no diagnosis is reached in up to 50% of cases. In general, infection accounts for one-fourth of cases of FUO, followed by neoplasm and noninfectious inflammatory diseases. FDG-PET is a sensitive diagnostic technique for the evaluation of FUO. Especially integrated imaging combining PET and CT facilitates anatomical localization of focally increased FDG uptake, thereby guiding further diagnostic tests to achieve a final diagnosis. FDG-PET/CT appears to be a more sensitive diagnostic tool in FUO than stand-alone FDG-PET, because of the precise anatomical localization of small lesions and better differentiation between physiological and pathologic metabolic foci. With FDG-PET/CT becoming widely available, FDG-PET/CT should be a routine procedure in the workup of FUO.

Section snippets

FDG-PET

Scintigraphic imaging is a noninvasive method allowing delineation of both the localization and the number of foci in all parts of the body based on functional or molecular changes of tissues and cells. It plays an important role in the diagnosis of patients with FUO in clinical practice. Conventional scintigraphic methods are 67Ga-citrate scintigraphy and 111In-labeled or 99mTc-labeled leukocyte scintigraphy. However, these techniques have their disadvantages and limitations, such as handling

FDG-PET in FUO

The value of FDG-PET has been studied in 3 retrospective and 6 prospective studies in 396 patients with FUO (Table 1).14, 15, 16, 17, 18, 19, 20, 21, 22 Two studies prospectively compared FDG-PET with 67Ga-citrate scintigraphy in patients with FUO and found FDG-PET to be helpful in 55%14 and 41%15of patients. In the study of Meller et al14 sensitivity, specificity, PPV, and NPV of FDG-PET were 81%, 86%, 92%, and 75%, respectively. A small retrospective study of 16 patients with FUO showed that

FDG-PET/CT in FUO

FDG-PET/CT in FUO has been investigated in 9 retrospective studies and 1 prospective study in 407 patients (Table 2).25, 26, 27, 28, 29, 30, 31, 32, 33, 34 Keidar et al25 investigated the role of FDG-PET/CT in a prospective study of 48 patients in FUO. PET/CT identified the underlying etiology of FUO in 22 patients (46%). Sensitivity was 100%, specificity was 81%, PPV was 81%, and NPV was 100%. In this prospective study, FDG-PET/CT was considered less helpful in the diagnostic process than in

Conclusions

Although scintigraphic techniques do not directly provide a definitive diagnosis, that is, a histologic or a microbiological diagnosis, they often provide the anatomical localization where a particular metabolic process is ongoing and with the help of other techniques, such as biopsy and culture, facilitate timely definitive diagnosis and therapy. On the basis of the data in the literature and the favorable characteristics of FDG-PET, conventional scintigraphic techniques should be replaced by

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