Diagnostic Use of Serum Ferritin Levels to Differentiate Infectious and Noninfectious Diseases in Patients with Fever of Unknown Origin

INTRODUCTION In this study, we determined whether serum ferritin levels could be used to differentiate between fever of unknown origin (FUO) caused by infectious and noninfectious diseases. METHODS FUO patients were hospitalized at Chonnam National University Hospital between January, 2005 and December, 2011. According to the final diagnoses, five causes were identified, including infectious diseases, hematologic diseases, noninfectious inflammatory diseases, miscellaneous and undiagnosed. RESULTS Of the 77 patients, 11 were caused by infectious diseases, 13 by hematologic diseases, 20 by noninfectious inflammatory diseases, 8 by miscellaneous diseases, and 25 were undiagnosed. The median serum ferritin levels in infectious diseases was lower than those in hematologic diseases and (median (interquartile range) of 282.4 (149.0-951.8) ng/mL for the infectious disease group, 1818.2 (485.4-4789.5) ng/mL for the hematologic disease group, and 563.7 (399.6-1927.2) ng/mL for the noninfectious inflammatory disease group, p=0.048, Kruskal-Wallis test). By comparison using the Mann-Whitney test, statistically significant differences were found only between the infectious disease and hematologic disease groups (p=0.049) and between the infectious disease and groups (p=0.04). CONCLUSION An optimal cutoff value of serum ferritin levels to predict FUO caused by a noninfectious disease (hematologic diseases, noninfectious inflammatory diseases) was established as 561 ng/mL.