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We examined the validity of the Personality Diagnostic Questionnaire--4+ (PDQ-4+) as a screening instrument for personality disorders among mentally ill prison inmates in Singapore. A total of 313 prison inmates completed the PDQ-4+ and the Structured Clinical Interview for DSM-IV Axis II Disorders (SCID-II). The subjects were 303 (96.8%) males and 10 (3.2%) females with a mean (SD) age of 40.7 (8.8) years. Kappa agreement between PDQ-4+ and SCID-II for the presence at least one personality disorder was moderate with high sensitivity and low specificity. For specific personality disorders and clusters, we found that the PDQ-4+ diagnosed more subjects as having each of the personality disorders than SCID-II with high negative predictive values. The area under the curve indicated moderate discriminatory capabilities. Our results suggest that the PDQ-4+ could be used as a potential screening instrument for personality disorders in prison inmates.

Although an operationalized and commonly accepted definition of maladaptiveness is lacking, the delineation of personality traits as being adaptive or maladaptive is essential in diagnosing personality disorders (PDs). A way to explore the meaning of maladaptiveness is to compare how patients from all DSM-III-R PDs relate to different traits and dimensions of various dimensional models of personality. In the present study, the Karolinska Scales of Personality (KSP) were used in a sample of 94 psychiatric outpatients who were assessed according to severity of maladaption and according to type of predominant cluster type of deviant traits. Only one of four factors of the scores of the KSP subscales, "Interpersonal Aversiveness," was related to degree of maladaption, indicating high detachment, suspicion, irritability, dysphoria, and low socialization as core features of maladaptiveness. Three subscales of the KSP Socialization were all associated with maladaptiveness. However, one subscale, "Childhood Adjustment," was also related to the predominant cluster type of personality pathology.

Three hundred consecutively admitted in- and outpatients were administered the Personality Diagnostic Questionnaire-4+ (PDQ-4+). The Structured Clinical Interview for DSM-IV Axis II Personality Disorders, Version 2.0 (SCID-II) was used as the external diagnostic standard for personality disorder (PD) assessment. SCID-II was administered blind to PDQ-4+ scores. Low agreement between PDQ-4+ and SCID-II was observed for both dimensional and categorical PD evaluations. Receiver operating characteristic (ROC) analysis showed a definitively satisfactory discriminatory capability only for two PDQ-4+ PD scales (dependent, and antisocial). In agreement with previous studies, these results showed that PDQ-4+ was not a substitute for a structured diagnostic interview.

The self-report Defense Style Questionnaire (DSQ) was designed to assess defenses along a developmental continuum. Factor analysis of the original DSQ suggested that the scale assessed four factors or types of defenses, whereas a more recent factor analysis indicated the DSQ measured three-factors: Immature, Neurotic, and Mature. No data, however, regarding the reliability or unique construct validity of DSQ dimensions was published. This article reports on factor analyses of two DSQ versions in a sample of 215 methadone maintenance patients. Results indicate that both DSQ versions are unidimensional, assessing only Immature defenses. The lack of published psychometric data raises concerns regarding the true reliability of DSQ dimensions reported in previous investigations. Prior statements based on DSQ findings may have been incorrect if the DSQ factors were unreliable. Findings from this investigation stress the importance of requiring and evaluating the psychometric integrity of an instrument before employing it in research.