The field of appropriate use criteria (AUC) or appropriateness criteria (ACR) is a framework used in healthcare to evaluate whether specific medical tests, procedures, or treatments are necessary or appropriate for a particular patient's condition. These criteria are developed by professional medical organizations based on clinical evidence and expert consensus. The goal of ACR is to ensure that healthcare resources are used efficiently and that patients receive the most appropriate care for their individual needs. ACR can help healthcare providers make informed decisions about which tests or treatments to recommend, leading to better outcomes for patients and potentially reducing unnecessary healthcare costs.