Development and evaluation of a treatment fidelity instrument for family-based treatment of adolescent anorexia nervosa

Treatment fidelity is defined as the extent to which a therapeutic intervention is delivered as intended, and its assessment is critical in order to evaluate the validity of inferences drawn regarding treatment effects. Despite being a key variable in outcome research, evaluation of treatment fidelity remains limited.(1-5.) In a 2007 review of 147 child and adult randomized controlled trials (RCTs) only 3.5% were described as adequately measuring fidelity (e.g. adequately establishing, assessing, evaluating and reporting treatment integrity).(6.) Furthermore, only a handful of studies examined fidelity in psychotherapy studies involving children and adolescents or in family therapy.(7-13.) In eating disorders treatment studies we found only four RCTs that provided data on treatment fidelity.(14-17.) The most common definition of fidelity focuses on adherence (defined as the utilization of specific procedures).(1; 3.) More recently, competence (defined as the level of skill or quality in delivering these procedures) has been added as a vital component of treatment fidelity. Additionally, fidelity relates to a specific treatment's differentiation from another treatment (i.e., proscribed practices).(1; 18.) There are several key variables that affect fidelity, including type of treatment (degree of difficulty, length, skills needed),(1.) patient characteristics (degree of pathology, motivation, readiness),(19.) therapist characteristics (training, experience, acceptability of the treatment, therapist/patient match)(1; 5.), and contextual issues that impact delivery (e.g., cost, resources needed, space needed, administrative support).(1; 4; 8.) While several studies provide support for the usefulness of family-based treatment (FBT) for adolescents with short duration anorexia nervosa (AN), only one report on therapist fidelity to the manualized form of treatment has been published.(14.) This study used a fidelity measure developed for FBT that assessed adherence only and for which no psychometric data are provided. The authors reported that therapist fidelity varied across treatment phases, with relatively good adherence in early treatment, which diminished in middle and late treatment. The report did not evaluate specific components of FBT purported to lead to clinical success (e.g., promoting parental alignment, externalization, use of a family meal, and psycho-education about the life threatening nature of AN), nor did it directly evaluate the skill or competency with which these interventions were carried out. Determining how best to assess fidelity in psychosocial treatments requires attention to several methodological weaknesses highlighted in the literature. First, procedures for evaluating fidelity using appropriate tools are highly variable. Further, the question of how best to assess competence (i.e. when and how often it must be assessed), will impact the nature of how fidelity and outcome are likely to be related over a course of treatment.(5; 20-22.) At the same time, ceiling effects of highly trained and supervised clinicians likely reduce variance on fidelity and therefore the likelihood of finding effects in RCTs.(23.) In addition, differences in the timing and measurement of outcome may also affect findings, with some studies suggesting early effects(24.), and others later ones.(8-10.) The development of a measurement tool that accurately and consistently captures treatment fidelity is needed to examine the impact of such variables on the fidelity-outcome relationship. Thus, the primary aim of this study is to describe the psychometric properties of an instrument designed to assess fidelity to early sessions of FBT.