Diagnosis and outcomes of fever of unknown origin cases with an erythrocyte sedimentation rate of 100 mm/h or more: An International ID-IRI (Infectious Diseases - International Research Initiative) Observational Retrospective Cohort Study.

Herein, we aimed to analyze the final diagnosis in a well-defined cohort of fever of unknown origin (FUO) cases whose erythrocyte sedimentation rate (ESR) was 100 mm/h or more during the admission. The subgroup of the FUO patients with an ESR of 100 mm/h or more during the FUO evaluation, was extracted from the study database of a previously published multicenter study (European Journal of Clinical Microbiology & Infectious Diseases. April 15, 2023;42 (4):387-98). Data for 139 patients (17.6%, 139/788 of the original cohort) who fulfilled the study inclusion criteria, were obtained from 29 centers from 11 countries. Infections, neoplasms, and noninfectious inflammatory diseases were found to be the reason of fever in [n = 74 (53.2%)], [n = 14 (10%)], and [n = 13 (9.3%)] of 139 patients, respectively. Regardless of the diseases subgroup top 6 diseases that were determined to be the reasons of FUO were tuberculosis [n = 15 (10.8%)], HIV/AIDS [n = 13 (9.3%)], urinary tract infection [n = 9 (6.5%)], infective endocarditis [n = 9 (6.5%)], lymphoma [n = 9 (6.5%)], and abscess [n = 9 (6.5%)]. The most common infectious diseases were tuberculosis (15/74, 20.2%), HIV/AIDS (13/74, 17.5%), and infective endocarditis (9/74, 12.1%), along with urinary tract infection [n = 9 (6.5%)] and abscess [n = 9 (6.5%)]. The most common noninfectious inflammatory diseases were adult onset Still disease (3/13, 23%) and giant cell arteritis, also known as temporal arteritis (3/13, 23%), and followed by polyarteritis nodosa (2/13, 15.3%). The most common neoplasm was lymphoma (9/14, 64.2%), followed by lung cancer (2/14, 14.2%). Reason of fever could not be defined in (29/139, 20.8%) patients. The invasive procedures were performed in (64/139, 46%) patients. Gender, age > 50 or not, and income level (high-middle-low) of the participating country were not associated with a significant difference in the final diagnosis category of the FUO case (P > .05). To the best of our knowledge, this is the first study evaluating the FUO in the subgroup of cases with extreme ESR elevation and infectious diseases comprised the most cause of the FUO in this particular subgroup.