The quality of data obtained by laboratory specialists and provided to the clinician should inspire confidence in both. The intensification of the supervision of the work in the medical analysis laboratory led to the definition of the complex concept of quality control and to the specification of the systems through which the action translates into fact. A successful medical act depends to a large extent on the accuracy of the results provided by the medical analysis laboratories. In the clinical laboratory practice, these investigations consist of three phases: 1. preanalytical phase (extra and intra-laboratory); 2. analytical phase; 3. the post-analytical phase. Specialty studies have shown that the proportion of errors in the pre-analytical phase reaches up to 80% [2].