Putting it all together, building the measurement uncertainty budget

We come to the final article of the series; well done if you have made it this far! The aim here is to summarise all the information covered in the preceding six articles. In doing so, we now have the skills to set, assess and review our measurement uncertainty in any situation in the clinical pathology laboratory. We will apply it here in a commonly encountered scenario – the implementation of a new assay. Please be aware that anything presented here is purely for demonstration purposes and, while it may not be an authentic uncertainty budget, the procedures we apply are those we will most often encounter in our work.

A new consultant begins his career in your department by wanting to implement the ‘serum rhubarb’ assay that was available at their previous hospital. They inform you that they would like it implemented as soon as possible.

We will assume that all the hard work of selecting an assay has been performed and we now have a new kit to begin to work up before placing into service. From Article 1 we know that there are a few simple questions that we can ask ourselves that allow us to define the measurand (Table 1). We are careful here as it is at this point that we can potentially introduce the most significant amount of uncertainty to our final result if it is not done properly.