Fever of Unknown Origin - Different Centuries, Different Patterns

Abstract
Background: Imaging techniques used in the last decades, and reported changes in various disease prevalence, may have dramatically influenced causes of Fever of Unknown Origin (FUO) Objectives: Our study’s objectives were to identify changes in prevalence and etiologies of FUO, since our previous study two decades ago, to clarify the most beneficial diagnostic strategies, and to investigate the long-term outcomes of undiagnosed and diagnosed patients Methods: Medical files with “fever” as a cause for admission and at least one-week hospitalization were evaluated. Patients were screened based on Petersdorf’s classic criteria. An interview was performed three months to twelve years after hospitalization Results: 3691 patients fit our primary selection criteria in 2004-2016; 141 patients fit Petersdorf’s criteria for FUO. The most common cause of FUO was infectious disease (39%), mainly bacterial (29%), though decreased from our previous study (39% vs 55%). There were dramatic increases in the incidence of malignancy (19% vs 7.9%) and inflammatory (20% vs 2%) etiologies and less undiagnosed cases (22% vs 32.7%). Weakness and weight loss were the most common co-complaints (80% all coexisted). Elevated ESR (97%), elevated CRP (95%) and anemia (80%), were the most common pathologic laboratory examinations found. Abdominal CT, blood cultures and serology proved to be the most valuable diagnostic tests. Long-term follow up interviews revealed that a final diagnosis was often reached during the patients’ next admission (20% out of 70%). 2% of patients died during the feverish episode and 34% died three months to twelve years after the episode Conclusions: Infections (mainly bacterial) remain the most common cause for FUO in southern Israel in the 21th century; although there is a remarkable increase in the rate of vasculitis and malignancy. When PET is not available, a thorough clinical examination including appropriate laboratory and imagine examination, as well as precise history taking are essential. Blood cultures and abdominal CT are the most useful diagnostic tests. Most undiagnosed cases resolved within days of discharge or are diagnosed in a following admission