Quality Control
Leo de Galan, Independent consultant, NetherlandsAbstract There are three levels of quality control with their unique testing procedures: control charts are used by analysts to measure the performance of their procedure, the blind duplicate is used by the lab supervisor to monitor the performance of his lab, and the proficiency test allows external organizations to measure the performance of a lab. The control chart and the cusum chart are prepared by analysts and plot the measured concentration of the reference material. A single statistically significant deviation from the known value indicates an out of control method. Blind duplicates test for excessive random error by presenting the analyst with two identical samples. If the measured concentrations differ by more than 2.8*s, the method warrants inspection. Finally, an external organization can conduct a proficiency test by distributing identical, homogenous samples to a number of laboratories, then measuring the individual laboratories’ deviation from the average measured value.
KeywordsControl chart, Blind duplicate, Proficiency test, Reference material, System suitability, Warning limit, Alarm limit, In control, Out of control, Cusum chart, t-Test, F-test, Z score, Intralaboratory reproducibility (r), Interlaboratory reproducibility (R)
LevelAdvanced
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