Investigation of diagnostic distribution and demographic data of patients followed with fever of unknown origin

Introduction: Fever of Unknow Origin (FUO) is defined as a temperature of 38,3 °C or higher with a minimum duration of three weeks without an established diagnosis despite at least one week's investigation in the hospital. Due to several factors that are not yet researched, the spectrum of the diseases that cause FUO diagnosis widely varies. Within these factors geographical prevalence patterns, the age of the patients, and difference in funding levels in developing and developed nations in FUO diagnosis may have significant importance. Hence, in this research we have reviewed the data on patients with initial FUO diagnosis and examined the follow up diagnosis of their diseases. We have documented the correlation between the initial FUO diagnosis and the final diagnosis considering patients demographic data. Procedure: In this study, the data on 125 patients who were admitted to the Istanbul Medical School Hospital – General or Emergency Internal Medicine Services- between January 2018 and September 2021 with FUO diagnosis are examined. For each patient his/her age, sex, birthplace, how long the patient is hospitalized, medical history, physical findings, complete bloodwork with bio-chemical values, imaging work, and interventional procedures are recorded and analyzed. Results: Our study included a total of 125 patients where 54 were women (43.2%) and 71 were men (56.8%), all with FUO diagnosis. A close assessment of the data shows that 35 patients (28.0%) were diagnosed as infection, 27 (21.6%) as NIID, 26 (20.8%) as malignant, 27 (21.6%) without a diagnosis, and 10 (8.0%) were grouped in "other" category. 28.5 % (n=10) of the patients in infection group were diagnosed as tuberculosis. Within the NIID group, 37.0%(n=10) had adult Still's disease. Within the malignant group, 50.0%(n=13) had Non-Hodgkin Lymphoma. 60% (n=6) of the patients in "other" group were diagnosed with subacute thyroiditis. We observed that a statistically significant number of PET-CT scan were done on patients in malignant group and all patients in this this group were determined to have PET uptake. In our study, we have discovered that 61.5% (n=16) of the patients in malignant group had lymph-node biopsy and 76.9% (n=20) had bone marrow biopsy. Such interventional procedures in the malignant group were statistically significantly higher than other groups. Conclusions: Our research results show that although the frequency of the FUO initial diagnosis for infections is decreasing, infections remain the largest category in the FUO diagnosis. Within the infections category, tuberculosis remains the most frequent infective cause. We have also observed that due to the increased use of serological and immunological tests NIID's rate in FUO is increasing. We have determined, PET-CT test is very beneficial in differential diagnosis of FUO particularly in malignancy.