The quality-costs of an analytical process: 2. A test yield formulation of the predictive value quality-costs model

A quality-costs model has been developed to predict the cost effectiveness of a batch analytical process subject to intermittent analytical errors. The process test yield (the proportion of analytical measurements in an analytical run that are reportable as patient test results) provides a useful measure of the efficiency of an analytical process and can be related to critical characteristics of the measurement and control procedures. Equations are provided to estimate test yield from the measurement procedure's frequency of medically important errors (f) and the control procedure's probabilities for error detection (ped) and false rejection (pfr). Examples illustrate how losses in process output depend on the characteristics of the measurement and control procedures, and how increased control efforts may actually improve the yield of analytical processes when the frequency of errors is high. The test yield formulation of the quality-costs model should aid efforts to provide more cost effective analytical processes.