The application of diagnostic thresholds plays an important role in the classification of mental disorders. Despite their importance, many diagnostic thresholds are set arbitrarily, without much empirical support. This paper seeks to introduce and analyze a new empirically based way of setting diagnostic thresholds for a category of mental disorders that has historically had arbitrary thresholds, the personality disorders (PDs). I analyzed data from over 2,000 participants that were part of the Methods to Improve Diagnostic Assessment and Services (MIDAS) database. Results revealed that functional outcome scores, as measured by Global Assessment of Functioning (GAF) scores, could be used to identify diagnostic thresholds and that the optimal thresholds varied somewhat by personality disorder (PD) along the spectrum of latent severity. Using the Item response theory (IRT)-based approach, the optimal threshold along the spectrum of latent severity for the different PDs ranged from θ = 1.50 to 2.25. Effect sizes using the IRT-based approach ranged from .34 to 1.55. These findings suggest that linking diagnostic thresholds to functional outcomes and thereby making them less arbitrary is an achievable goal. This study has introduced a new and uncomplicated way to empirically set diagnostic thresholds while also taking into consideration that items within diagnostic sets may function differently. Although purely an initial demonstration meant only to serve as an example, by using this approach, there exists the potential that diagnostic thresholds for all disorders could one day be set on an empirical basis.

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The purpose of this thesis was to investigate the psychometric properties of three global user subjective measures of the ”The Quality Star” clinical review model: Consumer Satisfaction Scale, Global Quality of Life scale, and Perceived Global Distress scale. The mental health implementation context of this review model emphasizes the client as an agent of change, taking part in shared decision making in an empowered role as collaborative partner to the professional clinicians. In Paper I study the patient self-rating Consumer Satisfaction Scale gave results comparable to those obtained by independent interviewer assessors. Out of cost-effective perspective professional time is saved and logistics simplified. In Paper II the visual analogue self-rating Global Quality of Life scale was shown to have satisfactory test-retest reliability, and concurrent validity with the “Life as a whole” item of Manchester Short Assessment of Quality of Life (MANSA). The patients’ conceptualizations of the scale based on associative findings with a number of validating instruments were consistent with expected areas of concern for Serious Mentally Ill persons. Similarly, in Paper III the visual analogue scale the Perceived Global Distress scale, showed acceptable clinical test-retest reliability, and concurrent validity with the MANSA item, “How satisfied are you with your mental health”. In associative analyses it was found that depressive, anxiety, interpersonal and existential elements contributed to the patient´s conceptualization of the construct. In Paper IV, a previous finding suggesting that women were more satisfied with the health care and had better social functioning compared to men was further elaborated investigating the discriminative properties of the subjective instruments. In the multi-centre cohort of 2552 patients it was possible to detect differences between genders and functional levels professionally assessed with the split version of Global Assessment of Functioning rating scale. The General discussion underlines that although subjective measures tend to have strong interrelations, supporting earlier findings, one has to use multiple measures for an optimal management of mental illness as the subjective outcome ratings have to be individually interpreted in a feed-back dialogue with the patient and be compared to observational assessments.