Dynamic deviation control in clinical chemistry laboratories based on the time variant behaviour of analytical processes.

Based on the time variant behaviour of analytical processes, a dynamic system of deviation control is discussed. Originating from industrial process control, measurability and controllability rules as measures of the optimum reconstructing and controlling efficiency of quality control systems are introduced. It is seen that when trying to reconstruct and control and analytical process, properties of the process and characteristics of the control system need to be taken into consideration. Application of these rules offers the possibility of investigating the effect of actions aimed at improving the performance of a controlling system, but also indicates if a certain precision requirement can be achieved with less effort and expense. An example illustrates the time variant behaviour of an analytical process used for urea determination in a clinical chemistry laboratory. It shows the applicability of measurability and controllability rules, with the emphasis on the measuring or reconstructing efficiency of the controlling system used in that laboratory for the surveillance of the urea determination.