Introduction.

The pre-analytical phase is a vital component of the clinical analysis algorithm. This involves a series of steps and procedures. Objective. To describe the level of compliance with the preanalytical indicators in the areas of chemistry and haematology of the clinical laboratory at a local Hospital in Caaguazú. Materiales y método. A non-experimental design and a mixed cross-sectional approach were applied. Three biochemists and one hundred patients were includer. Results. Our data was obtained by structured observation to patients and semi-structured interviews to three biochemists. The level of performance of the biochemists about the pre-analytical indicators presents both positive and negative aspects, of which the positive aspect stands out in 61% and 39% corresponds to aspects considered as deficient. The existing difficulties are the correct identification of the patient and the communication between the treating physician and/or technician, most of whom are unaware of the conditions in which they should present themselves for a medical examination. Conclusion. The correct performance, as well as their quality, in the pre-analytical phase, is directly related to the results obtained, which the requesting professionals will later use for decision-making, so it is an initial link that affects the entire subsequent process and must always be considered essential.