A protocol for the validation of qualitative methods of detection

Abstract

This paper presents a draft protocol for analyzing the results of validation studies for qualitative methods of detection which is designed to meet three competing goals: (1) to give correct answers, (2) have a broad scope of application, and (3) be accessible to a wide range of users. The draft protocol can be applied to the validation of methods by collaborative trial or to single-laboratory studies. The protocol produces an estimate of the probability of a positive response with a prediction interval within which 95% of laboratories (or analytical runs) are expected to fall when the method is applied in practice. The interval is calculated from the observed reproducibility (or within-laboratory reproducibility) standard deviation. Then a simple plot of prediction intervals for the probability of detection against the concentration of analyte, where the concentration is known, is used to provide an estimate of the range of limits of detection and false positive probability that we can expect to see when the validated method is applied in practice. The use of the draft protocol is demonstrated using results produced by three collaborative trials. A simulation study showed that a conclusion that a method is fit for purpose that is generated by the draft protocol is likely to be safe.