Psychometric properties of the Posttraumatic Diagnostic Scale (PDS) in alcohol-dependent patients

BACKGROUND: A high prevalence of comorbid posttraumatic stress disorder (PTSD) is found in patients with substance use disorders (SUDs). In the few existing studies, mixed results regarding the psychometric properties of common screening instruments for PTSD have been reported for patients with SUDs. No results are available for the Posttraumatic Diagnostic Scale (PDS), an established self-report measure for PTSD.

METHODS: The authors assessed 105 patients with alcohol dependence according to DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) (70% male) 2 weeks after their admission to an inpatient detoxification unit. Participants were administered the PDS, the PTSD module of the Structured Clinical Interview for DSM-IV (SCID), as well as measures of depression and anxiety. Patients with other substance use disorders were excluded as were patients reporting no traumatic event.

RESULTS: Internal consistencies were good to very good for the total scale (.93) and the subscales of the PDS (.82-.91). In our sample, the PDS had a high specificity (.89) but only moderate sensitivity (.57). Diagnostic agreement with the SCID was 83% (.46). The results of a receiver operating characteristic (ROC) analysis suggested that a PDS score of 8 was the optimal cutoff to screen for PTSD. The highest diagnostic agreement between PDS and SCID (89%; .60) was achieved using a cutoff score of 24.

CONCLUSIONS: These findings confirm previous results suggesting that the psychometric properties of self-report measures of PTSD in patients with SUDs might differ from those in the general population. When the PDS is used in recently detoxified patients with alcohol dependence, it seems advisable to modify the cutoff score of this instrument to improve its sensitivity and diagnostic accuracy.