The yield of total body CT in the workup of fever of unknown origin in hospitalized medical patients

Abstract

Introduction: Total body computerized tomography (TBCT) is frequently used as a diagnostic tool for fever of unknown origin (FUO) workup instead of a recommended fluorodeoxyglucose positron emission tomography FDG-PET/CT. We have assessed the TBCT diagnostic yield on a large, unselected cohort of patients with FUO.

Methods: We performed a single-center retrospective cohort study, examining all patients hospitalized in internal medicine between 2012 and 2019 with a documented fever and three negative blood cultures who subsequently had a total-body CT performed. After manually reviewing, we included 408 who met the criteria of FUO. We defined a positive study as a scan that led to the documented final diagnosis.

Results: A total of 164 patients (40.2 %) had a positive TBCT result. The majority of positive CT findings were of infectious etiologies (58.5 %), followed by neoplasms (22.8 %) and inflammatory disorders (14.0 %), with the chest (43.9 %) and abdomen (29.8 %) most affected. Using a logistic regression model, a positive scan results were associated with an elevated CRP (p<0.001). Decision tree analysis showed that 55 % of scans of patients with an elevated CRP (>6 mg/dL), low hemoglobin and high leucocyte count (>18000/ml) were positive. Patients without an elevated CRP had a positive scan in only 26 % of tests, and those with also an elevated albumin (>4 gr/dL) and low CRP had positive scan in only 11 % of cases.

Conclusions: TBCT has a clinically significant yield under specific clinical scenarios in medical patients with FUO- reaching 55 % in patients with an elevated CRP and leukocyte count and low hemoglobin. It is reasonable to proceed to TTBCT when FDG-PET/CT is unavailable and in well-defined clinical situations.

Keywords: Fever of unknown origin; Positron emission tomography FDG-PET/CT; Total body CT.