Validating existing clinical cut-points for the parent-reported Strengths and Difficulties Questionnaire in a large sample of Canadian children and youth.

Introduction: The Strengths and Difficulties Questionnaire (SDQ), for assessing behavioural and emotional difficulties, has been used internationally as a screening measure for mental health problems. Our objective was to validate the existing (British) SDQ cut-points in a sample of Canadian children and youth, and develop new Canadian SDQ cut-points if needed.

Methods: This study includes data from children and youth aged 6 to 17 years from the Canadian Health Measures Survey (n = 3435) and outpatient records from the Children's Hospital of Eastern Ontario (n = 1075). The parent-reported SDQ data were collected. We adjusted the existing SDQ cut-points using a distributional and receiver-operating characteristic (ROC) curve approach. We subsequently calculated the sensitivity, specificity and diagnostic odds ratio of the existing and new SDQ clinical cut-points to determine whether the new cut-points had better clinical utility, using both analytic approaches.

Results: Our data show differences in the screening effectiveness between the existing British and the Canadian-specific clinical cut-points. Specificity is maximized using the Canadian distributional cut-points, improving the likelihood of identifying true negative results. The total SDQ score met the threshold for clinical utility (diagnostic odds ratio > 20) using both the existing and new cut-points; however, the individual scales did not reach clinical utility threshold using either cut-points.

Conclusions: Future Canadian SDQ research should consider the new cut-points derived from our study population and the existing British cut-points to allow for historical and international comparisons.