Aim: For the accreditation of a medical laboratory, it is necessary to evaluate the quality indicators (QI) used to evaluate pre-analytical process performance and establish an infrastructure to prevent errors arising from outside the laboratory. We aimed to present the quality indicators to prove the pre-analytical process performance of a medical (clinical) laboratory that has a large workforce prepared for medical laboratory accreditation.

Methods: The sample rejection criteria were defined for the pre-analytical process. QIs, which are the requirements of the ISO15189 standard, was determined. QIs were estimated both as percentages and process Sigma levels. Pareto charts presented the distribution of errors.

Results: QI values calculated as “%” and “Sigma” levels consistently demonstrated performances. According to 80% cumulated percentages, the Pareto charts rankings were “haemolysed,” “coagulated,” “barcode error,” and “insufficient” samples. In addition, when Pareto charts were evaluated, it was seen that the first 2 reasons in the 6-month period were “hemolysis” and “clotted samples” in all months. Still, the third most common reason was found to vary between “barcode error” and “insufficient” samples.

Conclusion: Because of the consistency between % and sigma values, QIs can be presented with one of these in showing laboratory pre-analytical processes. However, sigma values give a more general view, and performance can be easily monitored between months. Pareto charts help illustrate error distribution and provide information for continuous improvement in laboratory-related healthcare.

Keywords: medical laboratory, accreditation, quality indicators, six sigma, laboratory error