Effect of liquid-handling accuracy on assay performance

This study illustrates how optimization of both liquid-handling accuracy and precision is critical to assay performance. The study was designed to examine (1) liquid-handling performance and (2) the effect of liquid-handling variability on two types of in vitro biochemical assays by making small but deliberate changes to assay volume delivery. Specifically, protein binding (streptavidin) and enzyme (α-galactosidase) assays were investigated by determining the effect of assay volume for each assay component. The concomitant effect of the liquid-handling variability was then measured via inhibitor potency and assay performance characteristics such as Z-factor, signal-to-background, and variability. It was found that small changes in assay component volumes were indeed measurable by potency (IC50) but not necessarily by assay variability (Z-factor). In fact, this study demonstrates how a miscalibrated liquid handler can lead to erroneous data.