Personality diagnostic questionnaire 4+ is not useful as a screener in clinical practice

In clinical practice, the combination of brief, cost effective, valid and reliable assessment of personality disorders (PDs) is highly important. Substantial budget cuts require optimal use of the clinician's time. PDs are related with high axis I comorbidity, poorer therapy outcome and increased health service costs. In an effort to find a screening questionnaire that meets both the demands of cost-effectiveness and methodological soundness, we investigated the use of the Personality Diagnostic Questionnaire 4+ (PDQ-4+) as a first step in a two-step diagnostic procedure. As the second step, we used the Structured Clinical Interview of DSM-IV Axis II Personality Disorders (SCID-II) as criterion measure. Our results show that the positive predictive power of the PDQ-4+ is rather low, resulting in a large number of false positives. Therefore, its added value is poor in comparison with administering the SCID-II in the first place. Also, the value of the two validity scales of the PDQ-4+ is highly questionable. We therefore conclude that the PDQ-4+ should not be used in clinical practice as a screening instrument for PD assessment.