A therapeutic trial involves administering a specific remedy to a patient without a clear diagnosis. The presence or absence of change is used to confirm or exclude a diagnosis.
When a therapeutic trial can be helpful:
(1) fairly certain of a diagnosis but atypical or unexpected features are present
(2) lack of diagnostic resources
(3) there are several possible diagnoses with no clear evidence for a single one
(4) the therapy is both sensitive and specific for the diagnosis
(5) there is reliable way to determine efficacy
Disadvantages of the approach:
(1) false negative response (the trial may fail even though the diagnosis was correct)
(2) false positive response (improvement unrelated to intervention)
(3) a failed test can further muddy up a confusing diagnostic situation
(4) subject to bias since not blinded
(5) adverse effects of intervention
