Quality indicators and specifications for key analytical-extranalytical processes in the clinical laboratory. Five years' experience using the Six Sigma concept.

Background: The results of 5 years of experience (2004-2008) with process-based quality management using quality indicators for key laboratory processes (analytic and extra-analytic) in a group of clinical laboratories affiliated with the Catalan Health Institute are presented. Our purpose was to analyze the evolution of the indicators, identify processes that require corrective measures, and obtain specifications that are more robust than the preliminary ones proposed in a previous study by the same group.

Methods: The yearly average was recorded for each indicator in each laboratory, the yearly interlaboratory median was calculated, and the changes occurring were studied to determine their continuity in the 5-year period. For each indicator, the average of the yearly medians was calculated and the results transformed to the Six Sigma scale to estimate the degree of control over the related process. It was suggested to establish the yearly interlaboratory median as the desirable specification for each indicator.

Results: The medians for most indicators were stable during the period studied. Thus, the specifications proposed in the first study were considered robust in these cases. The Six Sigma statistic provided added value in this study because it enabled detection of processes that should be improved, in which case the specifications proposed were considered provisional despite their stability. After identifying processes that have the greatest impact on patient safety, the group set a specification of 0%, regardless of the actual specification obtained, although the members are conscious of the difficulty in attaining this level of quality. Certain processes that are in a period of change obtained specifications that are considered in a phase of consolidation.

Conclusions: The results for indicators related with sample collection indicate that the process is stable and well controlled. However, based on the results for Hemolyzed serum sample, the group saw the need for installing centrifuges in all phlebotomy centers and established a recommendation to unify the system for measuring hemolysis. The indicator External control exceeds acceptance limit clearly highlighted the need to rigorously monitor the analytic phase of the clinical laboratory. The values obtained for the indicator Reports from referred tests exceed delivery time show that there is considerable deviation regarding the expected report delivery time, whereas for in-house laboratory reports, delivery time is satisfactory.