Description

To study effects, the investigators aim to conduct a randomized controlled trial (RCT) comparing blended treatment to an evidence-based face-to-face TF-CBT protocol, Prolonged exposure.

Data will be collected concerning symptoms of PTSD with the PTSD Checklist for Diagnostic and Statistical Manual 5 (DSM-5; PCL-5) which will be the primary outcome measure. Further, symptoms of PTSD will be measured with Clinician-administered PTSD Scale for DSM-5 (CAPS-5), depression The PHQ-9, symptoms of anxiety with GAD-7 , quality of life with Work and social adjustment scale (WSAS), and sleep with the insomnia severity index (ISI). Outcome measures will be distributed before, during, after, as well as 12-months following treatment.

To analyze the data, a non-inferiority analysis will be applied for the primary outcome variable. Step one in this analysis will be to determine what difference in mean scores on the PCL-5 between the two treatments is tolerated to conclude that the interventions are equally effective (non-inferiority margin). When comparing treatment effects a one-sided t-test with a 95% confidence interval will be used to investigate whether the lower limit of the interval for the experimental treatment (blended treatment) lays outside the non-inferiority margin. If the lower limit is within the non-inferiority margin the experimental treatment is interpreted to be non-inferior to the standard treatment (TF-CBT).

The value of our non-inferiority margin will be based on the established minimum change in scores required for a reliable change on the primary outcome measure as well as the effect size (Cohen's d) seen in a previous TF-CBT study (29). As a first step to determine our non-inferiority margin the investigators made a calculation entailing the following estimates: The post treatment score on the primary measure from the reference treatment which was 15.80 with a standard deviation of 15.97 (we assumed that our treatment would yield the same post-score). 7 which is the score in between the established minimal difference on the primary outcome measure required for a reliable change (reliable change = between 5 and 10 points). 7 points on the primary outcome measure is thus the non-inferiority margin in actual scores. Appointing these figures in an effect size calculator yielded the result of 0.4. This indicates that while expecting a zero difference in effect size between the two treatments in comparison, the tolerated non-inferiority margin in Cohen's d is 0.4.

Further, to estimate the required sample size, rigorous power calculations were carried out in collaboration with an expert in statistical analysis, applying a simulation-based approach using a 2-level linear mixed-effects model, using estimates from the reference TF-CBT looking at six assessment points. Variance components that were incorporated into the analysis were random intercept, random slopes and residual variance. The power calculation showed that with 78 participants in each treatment group and a 20% dropout rate 80% power is reached, given a non-inferiority margin of 7 points and α = 0.05.

Continuous data will be analyzed using mixed effects models or t-tests, dichotomous data using chi-square tests. In mixed effects model analysis of between-group differences, the interaction effect of group and time will be the central estimate. The investigators will also calculate effect sizes using Cohen's d based on pooled standard deviations. Remission rates will be calculated using a cut off of 38 on the PCL-5. The proportion of patients who will make a clinical significant change and reliable change according to the Jacobson and Truax algorithm will be measured. Dichotomous data of remission will also be analyzed with survival analysis where time to remission is calculated and compared between groups.