Quality control in the Netherlands; todays practices and starting points for guidance and future research.

OBJECTIVES: Adequate analytical quality of reported results is primarily ensured by performing internal quality control (iQC). Currently, several different iQC practices are in use. As a prelude to the revision of a Dutch guidance document on analytical QC, a questionnaire was sent out to gain insights in the applied practices and the need for guidance. METHODS: A questionnaire, containing 20 multiple-choice questions with possibilities for explanation and comment on iQC practices and aspects was distributed to all clinical chemistry laboratories within the Netherlands. Results were reported descriptively. RESULTS: Responses were received from 27 clinical laboratories (response 43 %). In 30 % the iQC was based on the analytical characteristics only, while 30 % used a 6-Sigma method, 19 % risk-based beyond 6-Sigma and 22 % used an alternative approach. 89 % of laboratories used a virtual analyzer model for iQC setup within one or more laboratory sites. Practices for determining standard deviation (SD) values included determining SD for each new iQC material (35 %), using historical SD values for new materials (35 %), and incorporating clinical tolerances into the SD value (31 %). Furthermore, 44 % of laboratories used patient moving averages for one or more tests. Daily iQC management was based on either "traffic lights" indicating in or out of control status, and review of all QC charts, often using multiple software systems. CONCLUSIONS: A large heterogeneity of iQC practices in clinical laboratories was observed in the Netherlands. Several starting points for further research and/or guidance were identified, particularly in relation to the determination of SD values, the virtual analyzer model and methods to ensure analyzer equivalence.

Performance specifications and six sigma theory: Clinical chemistry and industry compared.

Analytical performance specifications are crucial in test development and quality control. Although consensus has been reached on the use of biological variation to derive these specifications, no consensus has been reached which model should be preferred. The Six Sigma concept is widely applied in industry for quality specifications of products and can well be compared with Six Sigma models in clinical chemistry. However, the models for measurement specifications differ considerably between both fields: where the sigma metric is used in clinical chemistry, in industry the Number of Distinct Categories is used instead. In this study the models in both fields are compared and discussed.