Temperature over 37.8 °C at least once each day |
Duration of fever over 2 weeks |
Lack of evidence of infection (physical examination, laboratory examinations, imaging studies) |
Absence of allergic mechanisms (drug allergy, transfusion reaction, and radiation or chemotherapeutic drug reaction) |
Lack of response of fever to an empiric, adequate antibiotic therapy for at least 7 days |
Prompt complete lysis of fever by the naproxen test with sustained normal temperature while receiving naproxen |