Pre-analytical errors management in the clinical laboratory: a five-year study

Introduction: This study describes quality indicators for the pre-analytical process, grouping errors according to patient risk as critical or major, and assesses their evaluation over a five-year period. Materials and methods: A descriptive study was made of the temporal evolution of quality indicators, with a study population of 751,441 analytical requests made during the period 2007-2011. The Runs Test for randomness was calculated to assess changes in the trend of the series, and the degree of control over the process was estimated by the Six Sigma scale. Results: The overall rate of critical pre-analytical errors was 0.047%, with a Six Sigma value of 4.9. The total rate of sampling errors in the study period was 13.54% (P = 0.003). The highest rates were found for the indicators "haemolysed sample" (8.76%), "urine sample not submitted" (1.66%) and "clotted sample" (1.41%), with Six Sigma values of 3.7, 3.7 and 2.9, respectively. Conclusions: The magnitude of pre-analytical errors was accurately valued. While processes that triggered critical errors are well controlled, the results obtained for those regarding specimen collection are borderline unacceptable; this is particularly so for the indicator "haemolysed sample".