Why use a multiplex assay?
The main advantage of a multiplex assay, of course, is that you can analyze multiple proteins simultaneously rather than having to run multiple assays to look for each protein separately.
Running multiple assays means that there could be subtle variations in each run, which may impact the results. Running one assay prevents this variation from having a significant effect so that any difference seen in the levels of various proteins is more likely to reflect the true abundances within the sample.
Another disadvantage of running multiple single assays is this will require more sample. This may not be a problem if the sample is easy to obtain, however, some biological samples are not typically available on mass, thus, reducing the amount of sample needed for assays is a huge advantage. In this instance, multiplex assays can be very beneficial as it is possible to detect and quantify multiple proteins from a smaller sample volume.