This invention relates to a low cost rapid response diagnostic system to determine cortisol levels in patients selected as potential candidates for GCR (glucocorticoid receptor) antagonist therapy utilizing a GCR antagonist, such as ORG 34517. The rapid, sensitive, and inexpensive test can be used to determine patients who have non-normal cortisol production or disordered circadian rhythms as a method for selecting subjects for GCR antagonist therapy for whom it is likely to have beneficial and/or therapeutic effects, and can also be used to monitor changes in cortisol levels in response to treatment.