Epidemiological, clinical and prognostic investigation of fever of unknown origin cases, followed up as inpatients in our clinic between 2017 and 2024

Objective: The aim of this study was to reveal the etiological distribution of fever of unknown origin (FUO), physical examination, laboratory and imaging findings leading to diagnosis and the prognostic course of the cases. Materials and Methods: Between 2017 and 2024, 100 patients hospitalized in our clinic with a preliminary diagnosis of FUO were included in the study. Data were reviewed retrospectively. Age, gender, history, physical examination, laboratory examinations, imaging, interventional examinations, duration of diagnosis and hospitalization, and post-discharge prognosis data were recorded. Results: Of the 100 cases, 39 had collagen-vascular disease, 19 had infectious disease, 17 had malignancy, 12 had other diagnoses, and 13 could not be diagnosed. Vasculitis was the most common cause in the collagen-vascular disease group with 25.6%, and tuberculosis was the most common cause in the infection group with 36.8%. The most common malignant cause was lymphomas with 52.9%. In the other group, subacute thyroiditis was found in the first place with 25%. In the regression analysis performed for the malignancy group, it was determined that anti-HIV positivity, CRP of 140 mg/L and above and low haemoglobin values could be effective in predicting malignancy. Ferritin values of 875 μg/L and above were found to be significant in favor of malignancy (p:0.01). It was found that PET-CT contributed to the diagnosis of malignancy and infectious diseases at a statistically significant rate (p:0.004). A total of 11 cases, 7 of which were malignancy cases, were found to be exitus after discharge. Conclusion: With the improved diagnostic methods, the frequency of infections in the etiology of FUO has decreased, and the frequency of collagen-vascular cases has increased. Malignant cases are still important due to their incidence and poor prognosis. Early diagnosis in the malignancy and infection group is important in the prognosis of the patient. Due to the statistically significant (p:0.004) contribution of PET-CT to the diagnosis of malignancy and infectious diseases, early use of PET-CT in FUO cases should be considered. Keywords: FUO, tuberculosis, vasculitis, PET-CT, HIV