Design of an RCT on cost-effectiveness of group schema therapy versus individual schema therapy for patients with Cluster-C personality disorder: the QUEST-CLC study protocol

Abstract

Background Given the high prevalence of Cluster-C Personality Disorders (PDs) in clinical populations, disease burden, high societal costs and poor prognosis of comorbid disorders, a major gain in health care can be achieved if Cluster-C PDs are adequately treated. The only controlled cost-effectiveness study published so far found Individual Schema Therapy (IST) to be superior to Treatment as Usual (TAU). Group ST (GST) might improve cost-effectiveness as larger numbers can be treated in (>50%) less time compared to IST. However, to date there is no RCT supporting its (cost-) effectiveness. The overall aim of this study is to assess the evidence for GST for Cluster-C PDs and to improve treatment allocation for individual patients. Three main questions are addressed: 1) Is GST for Cluster-C PDs (cost-)effective compared to TAU? 2) Is GST for Cluster-C PDs (cost-) effective compared to IST? 3) Which patient-characteristics predict better response to GST, IST, or TAU? Methods In a multicenter RCT, the treatment conditions GST, IST, and TAU are compared in 378 Cluster-C PD patients within 10 sites. GST and IST follow treatment protocols and are completed within 1 year. TAU is the optimal alternative treatment available at the site according to regular procedures. Severity of the Cluster-C PD is the primary outcome, assessed with clinical interviews by independent raters blind for treatment. Functioning and wellbeing are important secondary outcomes. Assessments take place at week 0 (baseline), 17 (mid-GST), 34 (post-GST), 51 (post-booster sessions of GST), and 2 years (FU). Patient characteristics predicting better response to a specific treatment are studied, e.g., childhood trauma, autistic features, and introversion. A tool supporting patients and clinicians in matching treatment to patient will be developed. An economic evaluation investigates the cost-effectiveness and cost-utility from a societal perspective. A process evaluation by qualitative methods explores experiences of participants, loved ones and therapists regarding recovery, quality of life, and improving treatment. Discussion This study will determine the (cost-)effectiveness of treatments for Cluster-C PDs regarding treatment type as well as optimal matching of patient to treatment and deliver insight into which aspects help Cluster-C-PD patients recover and create a fulfilling life. Trial registration Dutch Trial Register: NL9209. Registered on 28-01-2021,

G-FORCE: the effectiveness of group psychotherapy for Cluster-C personality disorders: protocol of a pragmatic RCT comparing psychodynamic and two forms of schema group therapy

“…A random sample of 20% of the treatment session recordings will be rated by independent trained judges blind for condition. For GST-C, an existing adherence and competence measure will be used, the Group Schema Therapy Integrity Scale (GST-TI; see [ 43 ] and expanded. For SFGT, a new rating scale is developed, based on the Group Schema Therapy Rating Scale-Revised (GSTRS-R, [ 105 ].…”

“…For patients with a main diagnosis 'otherwise specified PD' with predominantly Cluster-C traits, a personalized selection of the Cluster-C traits derived from the AVPDSI, OCPDSI and DEPDSI is made. Psychometric qualities of these instruments are still under research, but excellent interrater agreement (ICC > 0.90) and internal consistency (Cronbach’s a > 0.90) is established [ 43 ]. Total scores of the AVPDSI, DEPDSI and OCPDSI consist of a total sum of the average symptom scores per subsection of the interview, an average burden score and an average impact score.…”

“…Preliminary observations from an ongoing RCT on patients with avoidant PD and Social Anxiety Disorder [ 8 ] suggests it is feasible and effective for this patient group. In another running multi-centre RCT, GST-C is compared with individual schema therapy and TAU [ 43 ].…”

Individual psychotherapy for cluster-C personality disorders: protocol of a pragmatic RCT comparing short-term psychodynamic supportive psychotherapy, affect phobia therapy and schema therapy (I-FORCE)

“…For patients with a main diagnosis otherwise specified PD with predominantly Cluster-C traits, a personalized selection of the Cluster-C traits derived from the AVPDSI, DEPDSI and OCPDSI is made. These interviews have excellent interrater agreement (ICC>.90) and internal consistency (Cronbach a >.90) [ 44 ]. The interviews are modelled after the Borderline Personality Disorder Severity Index (BPDSI), measuring the severity of BPDs.…”

“…Total scores of the AVPDSI, DEPDSI and OCPDSI consist of a total sum of the average symptom scores per subsection of the interview, an average burden score and an average impact score. The scores on the instruments are converted into one severity score by standardizing the raw scores (see Groot et al [ 44 ] for a description of the calculations per interview). To ensure quality of data collection of the AVPDSI, DEPDSI and OCPDSI, assessors will be trained, and all measurements will be audiotaped.…”