Measuring Treatment Response in Pediatric Trichotillomania: A Meta-Analysis of Clinical Trials

In clinical trials of pediatric trichotillomania (TTM), three instruments are typically employed to rate TTM severity: (1) the Massachusetts General Hospital Hair Pulling Scale (MGH-HPS), (2) the National Institute of Mental Health Trichotillomania Severity Scale (NIMH-TSS), and (3) the Trichotillomania Scale for Children (TSC). These instruments lack standardized definitions of treatment response, which lead researchers to determine their own definitions of response post hoc and potentially inflate results. We performed a meta-analysis to provide empirically determined accuracy measures for percentage reduction cut points in these three instruments. MEDLINE was searched for TTM clinical trials. A total of 67 studies were initially identified, but only 5 were clinical trials focused on TTM in pediatric populations and therefore were included in this meta-analysis (n = 180). A Clinical Global Impressions Improvement score ≤2 was used to define clinical response. Receiver operating characteristic principles were employed to determine accuracy measures for percentage reduction cut points on each one of the instruments. Meta-DiSc software was employed to provide pooled accuracy measures for each cut point for each instrument. The Youden Index and the distance to corner methods were used to determine the optimal cut point. The optimal cut points to determine treatment response were a 45% reduction on the MGH-HPS (Youden Index 0.40, distance to corner 0.20), a 35% reduction on the NIMH-TSS (Youden Index 0.42, distance to corner 0.17), a 25% reduction on the TSC child version (TSC-C; Youden Index 0.40, distance to corner 0.18), and a 45% (distance to corner 0.30) or 50% reduction (Youden Index 0.33) on the TSC parent version (TSC-P). The TSC-C had less discriminative ability at determining response in younger children in comparison to older children; no age-related differences were observed on the TSC-P. This study provides empirically determined cut points of treatment response on three instruments that rate TTM severity. These data-driven cut points will benefit future research on pediatric TTM.