The Personality Diagnostic Questionnaire has been through several revisions since its inception and the latest edition is called the Personality Diagnostic Questionnaire—Fourth Edition Plus (PDQ-4+; Hyler, 1994), which is consistent with the DSM-IV. The PDQ-4+ assesses the 10 standard personality disorders in the DSM-IV and the "plus" indicates that the measure also assesses Passive-Aggressive Personality Disorder and Depressive Personality Disorder in Appendix B of the DSM-IV. The PDQ-4+ contains 99 self-report, true-false items and takes about 30 minutes to complete. It has two validity scales: the Too Good scale measures underreporting of pathological personality traits, whereas the Suspect Questionnaire scale detects lying and random responding.
Due to the excess number of false positives associated with earlier versions of the measure, an optional Clinical Significance scale was designed for the PDQ-4+ to help the clinician assess whether the abnormal traits endorsed by the respondent (a) meet the diagnostic threshold for causing distress or impairment in the person's life, (b) are both pervasive and persistent, and (c) are not due to a current Axis I condition (Bagby & Far-volden, 2004).
The PDQ-4+ has a limited theoretical foundation. Rather, it was designed to be directly linked to the DSM-IV and, conse quently, each item on the measure corresponds to a single DSM-IV diagnostic criterion for a personality disorder. A "true" response to each item indicates that it is to be scored as pathological (and there are no reverse-scored items; Hyler, 1994). Scores are summed to indicate the number of criteria endorsed for each personality disorder, which can be used for tentative diagnosis. In addition, a total score consisting of the sum of all pathological items endorsed can be generated. This total score is an index of overall personality dysfunction (Hyler, 1994). Due to its simplicity, the PDQ-4+ can be hand scored although computer administration and scoring are available. The measure can be used in both normal and clinical populations and provides both dimensional and categorical scores for the disorders. Regarding psychometric properties of the PDQ-4+, the primary concerns seems to be a high false-positive rate and poor validity of the validity scales (Bagby & Farvolden, 2004). However, the measure does seem to have a low false-negative rate. As such, the measure is probably best viewed as a screening instrument in which tentative diagnoses must be followed up by more comprehensive patient assessment. Due to the low false-negative rate, PDQ-4+ might be helpful in ruling out personality disorders. Notably, there is no manual for the PDQ-4+ (which is problematic) and there are no imminent plans to revise the measure.
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