Final answer:
NCDs serve the purpose of spelling out CMS policies on when Medicare will pay for items or services.
Step-by-step explanation:
The purpose of NCD (National Coverage Determination) is to spell out CMS policies on when Medicare will pay for items or services. It provides guidelines for Medicare coverage and determines the conditions in which Medicare will pay for specific medical items or services. NCDs are developed based on clinical evidence and are used to ensure that Medicare beneficiaries receive medically necessary and appropriate care.