Protocols for the diagnosis and treatment of clinical conditions are matters for the attending doctor and his-her patients. The use of any particular diagnostic test such as the RAST test, either in its own right or as an alternative to another test, would be a decision that a doctor and a patient would make given the nature of the condition involved and, in particular, any specific features which would characterise the individual patient's clinical presentation. The RAST test is an allergen specific IgE antibody test which can be used when there are signs or symptoms suggestive of an allergy to one or more substances or foods.
The use of particular diagnostic tests should be based on the best available evidence on such properties as their sensitivity, specificity, effectiveness and cost effectiveness. This evidence is described in the international medical literature, any recommendations emanating from standards or training bodies or expert scientific groups and, of course, the doctor's own experience, skills and knowledge of the patient.