Premise: A patient with fever due to cancer will show clinical improvement with fall in body temperature while a person with some other cause will not improve.
As with many clinical tests there is a need to be cautious in how this information is interpreted. False positives and false negatives occur with some frequency. In the right circumstances it can be helpful.
Its performance can be improved by increasing the pre-test probability:
(1) selecting patients who are thought to have an underlying tumor
(2) selecting patients with persistent fever
(3) performing a number of tests to identify a patient with infection (blood culture, urine culture, chest X-ray)
Reasons for failure of the naproxen test in a patient with cancer-related fever:
(1) large amount of necrotic tumor
(2) concurrent sepsis (mixed causes)
(3) insufficient dose of the NSAID (Economos et al used 250 mg po tid)
(4) noncompliance
