Unexplained fever and chronic fatigue: abnormal circadian temperature pattern.

OBJECTIVES: Standard clinical and biological investigations can be used to determine the origin of persistent and moderate fever in a large number of otherwise asymptomatic patients. However, in a small proportion of cases, isolated fever and fatigue persist despite the absence of detectable organic malfunction. This study was conducted to investigate the circadian thermic pattern in patients with apparently unexplainable fever and chronic fatigue and in those with fever of recognized origin. METHODS: We recorded central temperature continuously for 24 hours in patients with moderate fever of both unexplained and recognized origin, and in a control group of healthy volunteers. A Fourier series was used for harmonic analysis. RESULTS: Thermic patterns specific to the three groups were identified by statistical and factorial analysis. The patients with fever of unknown origin and chronic fatigue were clearly characterized in terms of the phase, amplitude of the first (fundamental) harmonic and minimum circadian temperature. CONCLUSION: The abnormal central temperature pattern in these patients may prove to be an important step in the management of febrile patients.