We define a procedure as necessary – or crucial – if all four of the following criteria are met:
• The procedure must be appropriate, as defined… [with a median rating on an appropriateness scale of 7-9m without disagreement].
• It would be improper care not to recommend this service.
• There is a reasonable chance that the procedure will benefit the patient. Procedures with a low likelihood of benefit but few risks are not considered necessary.
• The benefit to the patient is not small. Procedures that provide only minor benefits are not necessary

… In conclusion, necessity ratings can be used together with appropriateness ratings to address not only the overuse of procedures but also to indicate limited access to care through underuse of procedures. Key words: appropriateness; necessity; crucial; guideline panels.