Failure Mode and Effects Analysis FMEA is the most appropriate tool in this scenario because it is a proactive risk assessment methodology designed to identify and mitigate potential failures before harm occurs. According to Health Care Risk Management principles outlined by ASHRM and the American Hospital Association Certification Center, FMEA is specifically used when introducing new processes, services, or high-risk clinical operations, such as an anticoagulation clinic involving medications with narrow therapeutic indices and significant bleeding risks.

FMEA systematically evaluates each step in a proposed process, identifies possible failure modes, analyzes their causes and effects, and prioritizes risks using severity, occurrence, and detectability scoring. This structured approach aligns with patient safety objectives by reducing preventable adverse events before implementation.

In contrast, Root Cause Analysis RCA is a retrospective tool used after an adverse event has occurred. A cause and effect diagram is a component often used within RCA or FMEA but is not a comprehensive risk assessment tool on its own. A scatter diagram is primarily used for statistical correlation analysis and does not evaluate process failures.

Therefore, for proactive risk identification and mitigation prior to clinic opening, FMEA is the best and most appropriate tool.