ABSTRACT
Even following the guidelines laid out in the previous chapters, anyone developing or running an assay will inevitably encounter problems, it would be dishonest to say anything different.
The 'breakdown' of any assay suggests that some variable has gone out of control. If it is not obvious what this variable is, and as a consequence it is difficult to get the assay working effectively again, then the assay contains some uncontrolled variable(s). In an ideal world these factors would have been identified and/or eliminated by following the procedures laid out in the chapters on assay development and validation. Time spent at the development stage using well planned experiments to investigate the major assay variables such as incubation temperature, incubation time, batch of protein additive etc., is time well spent, as this should ultimately reduce assay down time. However, to investigate every conceivable assay variable could take many months if not years of experimental work. Such investigation needs to be balanced against the likelihood of the assay failing, the consequences of this and the time taken to re-establish the assay.
