Application of Sigma Metric for Quality Improvement in Laboratory of Clinical Chemistry

Application of Sigma Metric for Quality Improvement in Laboratory of Clinical Chemistry

Alina Prodan, Dalius Vitkus

Introduction. One of modern labora­tory goals is to perform higher number of tests with less expenses achieving highest possible quality. Six Sigma method is a concept of basic quality im­provement geared towards a process standardization. Sigma metric is used in Six Sigma quality management as a universal measure of quality. This quality assessment approach is based on analysis of quality goals. Statistical results of quality control analysis have been widely used for study. Benefits of sigma metric for qual-ty goals evalua­tion have been shown. It was shown how significant improvement of quality control procedures can be to meet qual­ity goals.

Aim of the study - to assess ad­vantages of application of sigma metric for quality improvement in laboratory of clinical chemistry.

Results. 12 of 20 studied analytes results did not meet the desirable qual­ity goals. After applying sigma metric it was found, that ALAT and CK met the world class quality goals. Calculated sigma metric results according to strict quality goals (CV of calcium - 2.4%, chloride - 1.5%, sodium - 0.9%) were: calcium and chloride - negative sigma, sodium - 0.6 sigma. After applying two series of control measurements, 8 of 20 studied analytes results met the world class quality. After changing al­bumin’s calibrator, albumin sigma re­sults improved from negative to 3.9. For most analytes lowest sigma results were determined at low concentration lev els.

Conclusions. At the beginning of the study most of the stud-ed clin-cal chemistry analytes did not meet the recommended analytical quality goals. Sigma metric was used as quantitative measure to evaluate if the quality goals were met. Because of strict quality re­quirements, sigma values for some analytes were very low. After applying of two control measurements series per day, sigma metric results improved sig­nificantly. The importance of calibra­tion material has been shown. Sigma metric also described proportional de­viation of some studied analytes re­sults.

Keywords: quality control, sigma met­ric, quality requirements, clinical chemistry, quality goals.