The objective of this study was to evaluate the relationship between clinical features and the presence of infection on thoracic and abdominal tomography (CT) scans in emergency department (ED) patients with acute febrile illness without apparent source.

Patients aged 18 years and over who presented to ED with acute fever of unknown origin between January 1, 2020 and December 31, 2020 and underwent CT imaging (thoracic and abdomen) as a diagnostic test were included in the study retrospectively. Acute fever of unknown origin was defined as the absence of a history or physical examination finding that could explain the possible cause of fever, normal values of parameters that would suggest an infection in the urine analysis, and absence of infiltration on chest X-ray. The patients were divided into two groups according to the presence and absence of a source of infection on CT. The clinical and demographic data of the patients were evaluated. The effect of clinical factors on the presence of infection in CT scans was determined using the logistic regression analysis.

Among the 173 patients included in the study, the CT scans were positive for the source of infection in 31.2% (n = 54) and negative in 68.8% (n = 119). In the multiple logistic regression analysis, age ≥ 65 years [odds ratio (OR): 2.72, 95% confidence interval (CI):1.15–4.35, p < 0.001), presence of comorbidity (OR:2.37, 95%CI:1.08–4.14, p = 0.033), and procalcitonin positivity (PCT) (OR: 2.54, 95%CI: 1.29–4.95, p = 0.006) were identified as risk factors for the presence of infection in CT.

Patient's age, presence of comorbidity and PCT level should be considered when deciding on the use of CT in determining the source of infection in acute febrile patients without clinical clues.