Original article
Contribution of 18fluoro-deoxyglucose positron emission tomography to the work-up of patients with fever of unknown origin

https://doi.org/10.1016/j.ejim.2004.01.018Get rights and content

Abstract

Background: Recent studies have suggested that 18fluoro-deoxyglucose (FDG) positron emission tomography (PET) may be useful in the work-up of patients with fever of unknown origin (FUO), but its exact diagnostic yield has not been established. Methods: From January 1999 through December 2001, 74 (67%) of 110 prospectively collected patients who fulfilled the revised criteria of classic FUO underwent a FDG-PET scan. The diagnostic yield of this technique was assessed after diagnostic work-up and follow-up. Abnormal FDG-PET scans that pointed to the final diagnosis were categorized as helpful; all other scans were considered noncontributory. Results: A final diagnosis was established in 39 (53%) of the 74 patients who underwent FDG-PET. Fifty-three (72%) of the 74 FDG-PET scans were abnormal; 19 scans (36% of the abnormal scans or 26% of the total number of scans) were helpful. In the 39 patients with a final diagnosis, 49% of the scans were helpful. A diagnosis was established in 31 (58%) of the 53 patients with an abnormal scan and in 8 (38%) of the 21 patients with a normal scan (P=0.2). Baseline clinical variables (age and sex, as well as periodicity, duration, and height of the fever) and inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein, and hemoglobin) did not predict the usefulness of FDG-PET. Conclusions: FDG-PET contributed positively to the diagnosis in a quarter of our patients with classical FUO. This number is lower than that found in previous studies. Yet, against the background of the wide array of heterogeneous disorders that make up the FUO spectrum and the low number of final diagnoses established (in only 53% of cases), the diagnostic yield of FDG-PET is encouraging. Therefore, the use of FDG-PET should be considered whenever a baseline work-up fails to reveal the cause of a prolonged, febrile illness.

Introduction

18Fluoro-deoxyglucose (FDG) positron emission tomography (PET) has been established as a sensitive imaging technique in oncology, cardiology, and neurology [1]. Its role in infectious and inflammatory diseases is less defined, yet emerging. Our group and others have recently examined the contribution of FDG-PET in the work-up of patients with fever of undetermined origin (FUO) [2], [3], [4], [5]. Based upon our experience with FUO patients studied between 1996 and 1998, we advocated the early use of FDG-PET in patients with prolonged fever whenever first-line investigations failed to yield potentially diagnostic clues [2]. The present study encompasses the FUO patients who were prospectively collected and investigated in our center for 2 years after the end of the prospective pilot study of FDG-PET [2]. Hence, it can be considered as a validation of the diagnostic value of FDG-PET in patients with classical FUO. In addition, we sought to determine whether baseline clinical variables or inflammatory parameters could delineate a subgroup of patients in whom FDG-PET may be particularly useful.

Section snippets

Patients

From January 1999 through December 2001, we prospectively registered all patients who were seen at the department of general internal medicine of our university hospital and who fulfilled the revised criteria of classic FUO: duration of illness of more than 3 weeks before diagnosis, repeatedly documented body temperature exceeding 38.3 °C, and no diagnosis after 3 days of in-hospital investigation or three outpatient visits [6]. We excluded patients with nosocomial fever and with known HIV

Results

Of the patients in the prospectively collected register, 110 fulfilled the revised criteria of classic FUO (Fig. 1). The attending physicians ordered FDG-PET scintigraphy in 74 cases (68%). Table 1 compares baseline characteristics, laboratory parameters, final diagnosis, and duration of follow-up of these 74 patients with those of the 36 patients who did not undergo FDG-PET during the diagnostic work-up. In the patients without FDG-PET, median admission erythrocyte sedimentation rate and

Discussion

Prolonged febrile illnesses can be caused by a wide variety of disorders including infectious, neoplastic, and noninfectious inflammatory diseases [8], [9], [10], [11], [12]. Nuclear medicine can play a role in the diagnostic work-up by means of radioactive tracers that accumulate in focal disease processes and guide additional specific testing. Gallium-67 citrate has the potential to accumulate in both neoplastic and inflammatory, infectious as well as noninfectious, lesions. In a large

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