One primary means of refining the taxonomy of psychiatric illness is to test a particular taxonomy by observing if it has empirical utility.
And one of the most extensive methods of testing for empirical utility of a particular approach to psychiatric illness taxonomy is to observe its utility within an epidemiologic framework.
Please reference the discussion in Taxonomy of Psychiatric Illness.
There are several ways in which to go about making such determinations. The simplest is use a universal survey method of assessing for illness.
One classic approach to this, is to utlilize a diagnosis that has an unmistakable external stigmata (examples inlcude neurofibromatosis), and utilizing well known populations, determine the utility of surveys of poorly known populations to determine the quality of the survey.
In other words, the first step in psychiatric epidemiology is to determine a rating scale for various epidemiologic methods.