The classic definition of FUO from the early 1960s was: fever greater than 38 degrees Celsius on several occasions over a 3 week period of time with week worth of hospital investigations. With changes in our healthcare system, it is now generally accepted that the definition applies if only 2-3 weeks have past and there have been initial investigations performed (the list of which tests varies)
When thinking about FUO remember the 4 major categories
Inflammatory, Infectious, Malignancy and up to 50% do not end up with a diagnosis (and generally have a good prognosis)
A prospective study from the Netherlands illustrates this
A proposed algorithm based on existing evidence was created by a Toronto internist and published in Archives of Internal Medicine. Dont forget that investigations should be tailored/expanded based on a comprehensive history and physical.
