The role of the External Quality Assessment

External Quality Assessment (EQA) and Proficiency Testing (PT) are valuable tools in the quality improvement process. They provide objective evidence of laboratory competence for customers, accrediting bodies, and regulatory agencies, and serve as a unique source of information that is not obtainable in other ways. Traditional EQA/PT schemes tend to address only the analytical process (examination procedures), but some innovative schemes have been recently introduced to evaluate both pre- and post-analytical activities of the medical laboratory. The most important considerations in selecting an EQA/PT program include the evidence that: (i) samples are commutable (i.e. they behave like patient samples), (ii) reference values are traceable, (iii) method comparability with available peer groups is allowable, (iv) the size of peer group is statistically appropriate, and (v) both the timeliness and the usefulness of reports is granted. Careful evaluation of a single EQA/PT result should be coupled with active tracking of all results over time, and monitoring performances represent a challenging issue for medical laboratories. It is also important to consider that every EQA/PT scheme presents some limitations and that it is not appropriate to use EQA/PT as the sole means for evaluating laboratory quality. Therefore, there is the need to underline that internal quality control (IQC), EQA/PT and other tools have to be implemented and used to monitor and improve the quality in laboratory diagnostics.