Quantifying practice effects in longitudinal research with the WISC-R and WAIS-R: A study of children and adolescents with hemophilia and male siblings without hemophilia

Objective: To quantify practice effects associated with annual administrations of WISC-R and WAIS-R in children and adolescents with and without hemophilia. Methods: Participants were young men (age: 7-19; 80 with hemophilia, 30 siblings) enrolled in the Hemophilia Growth and Development Study. Participants with hemophilia completed age-appropriate Wechsler scales at baseline and at four annual follow-ups; the siblings, at baseline and one 2-year follow-up. Regression analyses were used to quantify average changes in scores, adjusting for variables related to test performance. Results: Consecutive annual evaluations were free of significant practice effects for 4 years with the Verbal Scale and for 2 years with the Performance Scale. VIQ decreased, and PIQ increased over time. Baseline VIQ was related to changes in VIQ; baseline PIQ and number of test-specific retests were related to changes in PIQ. Conclusions: The findings support use of Wechsler scales for annual evaluations to monitor cognitive development in children and adolescents.