"Classic" criteria of Petersdorf and Beeson:
(1) fever > 38.3°C on several occasions for > 3 weeks
(2) cause not identified after a hospital workup lasting 1 week or more
1991 revision of Durack and Street:
(1) fever > 38.3°C on several occasions for > 3 weeks
(2) cause not identified after a workup:
(2a) in hospital lasting 3 days or more
(2b) 3 or more outpatient visits
where:
• Imaging studies probably are not counted as an outpatient visit.
• In the implementation the number of hospital days is added to the number of outpatient visits. A workup in the hospital for 1-2 days plus an outpatient workup should count towards the total time requirement.
Factors affecting the efficiency of the evaluation:
(1) cost containment, with many workups now performed in the outpatient setting
(2) experience of the physician in selecting and interpreting the diagnostic tests
(3) specialty of the physician, which may affect if and when an invasive test is performed
(4) possible exposures that the patient may have had, especially occupational and travel related
