The document that clearly explains the patient's need for a DME item is a(n) ____.

The document that clearly explains the patient's need for a durable medical equipment (DME) item is a Certificate of Medical Necessity. This certificate serves as a formal justification from a healthcare provider indicating that a specific DME is essential for the patient's treatment or health management, based on their medical condition. It typically outlines the clinical rationale for needing the equipment, ensuring that insurers understand the medical necessity before approving coverage for the DME.

The other types of documents mentioned serve different purposes. A Medical Service Request Form generally facilitates communication regarding various services needed but may not specifically detail the need for DME. A Patient Care Report is typically used to document patient care and treatment details but does not focus on justifying medical equipment needs. A Referral Authorization Form is often used to obtain approval for referring a patient to a specialist or another provider, rather than for the necessity of equipment. Therefore, the Certificate of Medical Necessity is specifically designed to elucidate the need for DME, making it the correct choice.