Ensuring that assays give the same results on different platforms or in different laboratories is one of the most complex activities performed in laboratories. Whether the assay transfer involves scaling up an assay to a higher-throughput platform or moving an assay from a development to a quality control environment, assay transfer failures can result in significant delays in projects and manufacturing, additional costs, and incomparable data.
The following tips are designed to help facilitate assay transfers within and between laboratories.
Differences in equipment, reagent, technique, and interpretation of methodology are typically the focus of preparation before assay transfer. Less obvious variables, such as those that involve liquid handling, are frequently overlooked—the accuracy and performance of pipettes and automated liquid-handling instruments are often taken for granted and not given the proper attention they need.
By precisely describing each liquid-handling action, the critical liquid-handling steps can be identified and the critical parameters evaluated. This process will highlight any areas of the protocol that could prove problematic during assay transfer.
For assay data to be reliable, the amount of liquid dispensed needs to be both accurate and precise. Accuracy refers to how close the amount of liquid transferred is to the target volume, whereas precision tells us how close the repeated measurements in a group are to one another.
Implementation of verification checks prior to assay transfer ensures that the performance of the liquid-handling instrument is known and reduces the potential for failure. Additionally, regular calibration at both the transferring and receiving sites further minimizes the risk of error. If the performance of both the transferring and receiving liquid handling instruments is evaluated using the exact same method, the risk of error can be minimized as the results will be directly comparable.
Generating effective documentation is another critical part of pre-transfer work. A detailed standard operating procedure (SOP) describing the assay as it is executed in the transferring site is key because it provides a standard for training and implementation at the receiving site.
Robust and detailed SOPs created at the transferring site provide information that can further define assay steps to reduce problems at the receiving site. Detailing the liquid-handling steps outlined in Table 1 will make it easier for the receiving site to mimic the transferring site and will ultimately make a successful transfer more likely.
Another important component is the transfer protocol, which is a formal protocol defining the expectations for the transfer exercise. It provides agreement between the sites on how the transfer will be executed and defines the criteria for a successful assay transfer. A comparison between the results for identical samples at both sites is required, and an equal number of determinations for each sample at each site are advisable to simplify statistical analysis.