The Dialectical Behavior Therapy Adherence Coding Scale (DBT ACS): Psychometric Properties

The Dialectical Behavior Therapy Adherence Coding Scale (DBT ACS) is an observer-rated measure used to evaluate the extent to which therapists deliver individual and group DBT with adherence to the manual. Despite its frequent use in clinical trials of DBT, relatively little is known about its psychometric properties. The present study utilized data from six clinical trials conducted in research and community settings with a variety of patient populations. Across these studies, the DBT ACS was used to code a total of 1,271 DBT individual therapy sessions and 180 DBT group sessions. Results indicate the DBT ACS computed global score has good internal consistency (alpha = .81) and excellent interrater reliability (ICC = .93). A confirmatory factor analysis found that a single factor yielded acceptable goodness of fit indices. The DBT ACS discriminated between DBT and another treatment and between research and community therapists. Across studies, variability in adherence scores was attributable more to therapists (33%) than to patients (15%). Both therapist and patient variability were higher in effectiveness than efficacy trials. Generalizability coefficients indicated that 5 sessions are needed to estimate a dependable adherence score at the patient level, whereas 9-15 sessions are needed to achieve adequate generalizability at the therapist level. Fewer sessions were needed to yield dependable scores for community therapists compared to research therapists. The DBT ACS appears to be a reliable, valid, and dependable method of assessing therapist adherence to individual and group DBT across diverse treatment settings, therapist types, and patient populations.