Scales for assessing therapeutic adherence and competence in dialectical behaviour therapy for PTSD: development and analysis of psychometric properties

The assessment of therapeutic adherence and competence is essential to understand mechanisms that contribute to treatment outcome. Nevertheless, their assessment is often neglected in psychotherapy research.

To develop an adherence and a treatment-specific competence rating scale for Dialectical Behaviour Therapy for Posttraumatic Stress Disorder (DBT-PTSD), and to examine their psychometric properties. Global cognitive behavioural therapeutic competence and disorder-specific therapeutic competence were assessed using already existing scales to confirm their psychometric properties in our sample of patients with PTSD and emotion regulation difficulties.

Two rating scales were developed using an inductive procedure. 155 videotaped therapy sessions from a multicenter randomised controlled trial were rated by trained raters using these scales, 40 randomly chosen videotapes involving eleven therapists and fourteen patients were doubly rated by two raters.

Both the adherence scale (Patient-level ICC = .98; α_s= .65; α_p= .75) and the treatment-specific competence scale (Patient-level ICC = .98; α_s= .78; α_p= .82) for DBT-PTSD showed excellent interrater – and good reliability on the patient level. Content validity, including relevance and appropriateness of all items, was confirmed by experts in DBT-PTSD for the new treatment-specific competence scale.

Our results indicate that both scales are reliable instruments. They will be useful to examine possible effects of adherence and treatment-specific competence on DBT-PTSD treatment outcome.