Objective: Severity ratings of psychopathology in minors are often based on a composite score of the parent's and child's reports. However, parent's and child's reports often differ substantially, resulting in the integration method affecting the final scores. Nevertheless, effects of integration algorithms are seldom assessed and poorly understood. Method: The dataset is derived from the Treatment for Adolescents with Depression Study (TADS) and consists of 439 adolescents, 54% female, with a Major Depressive Disorder. The interviewer conducted the clinical interview Children's Depression Rating Scale-Revised (CDRS-R) with the parent and the adolescent and the TADS manual advised the interviewer to use the higher score as the final rating unless an informant was judged to be unreliable. Polynomial regressions, multivariate analyses, and mixed models were used to analyze the effects of this integration algorithm on the final scores and associated factors. Results: In 77% of the cases, the interviewer followed the TADS rating rule to use the higher CDRS-R item score. However, the final item scores differed significantly from the rule using the higher value, with the higher score being less often adapted at follow-up assessments and in female patients. Conclusions: The algorithm used to integrate divergent reports affects study outcomes and might introduce data-specific biases. Judgments of the validity and reliability of informants compromise the objectivity of outcomes in major clinical trials by introducing a subjective bias. Therefore, the agreement between children's and parent's reports and the method of integration should routinely be reported in research on pediatric psychopathology. ClinicalTrials.gov NCT00006286.
Keywords: CDRS-R; TADS; agreement; clinical trials; integration; interviewer.