Comparability, compatibility, equivalence and interchangeability: metrological concepts widely misunderstood in laboratory medicine

Distinguishing among comparability, compatibility, equivalence, and interchangeability is essential for the metrological interpretation of method-comparison studies and for ensuring safe analytical and clinical decision-making. Integrating these concepts explicitly into study design, harmonisation strategies, and reporting practice will strengthen traceability implementation, prevent erroneous claims of "agreement", and support more reliable patient care.