Examination of the Screening Properties of the Personality Diagnostic Questionnaire 4+(PDQ-4+) in a Prison Population

There is a high prevalence of personality disorder in most prison populations. Many pass through the system undiagnosed. A screening instrument would improve identification. This study examined the screening properties of the Personality Diagnostic Questionnaire-4+ (PDQ-4+) in prisoners convicted of violent and sexual offences. A sample of British prisoners completed the self-report PDQ-4+ and were interviewed using the Structured Clinical Interview for DSM-IV Axis II disorders. When used to generate a total score, the PDQ-4+ had an acceptable overall accuracy as measured by the area under the Receiver Operating Characteristics (ROC) curve. The PDQ-4+ appears to have the properties suitable for use as a screening instrument, particularly when screening for the presence or absence of personality disorder rather than for individual personality disorder categories. A graph is presented from which choices of cut-off score for different combinations of sensitivity and specificity can be made. A cut off total score of 25 or above yielded near optimal sensitivity and specificity. The suggested cut off score for this population is lower than that previously suggested.