The predictive validity of the learning disabilities index (LDI): A six-year longitudinal study

The present investigation examined the long-term predictive validity of Lawson and Inglis's (1984) Learning Disabilities Index (LDI) as it relates to achievement outcomes for a heterogeneous population of school-identified learning-disabled children. Results indicated that successive LDI scores at ages 7, 10, and 13 were capable of differentiating among children who had been identified as belonging to good, moderate, and poor outcome groups on the basis of FSIQ and WRAT scores obtained at age 13. A significant age by outcome group interaction emerged, in which the good outcome group displayed consistent but low LDI scores, the moderate group displayed an increase in LDI scores between the ages of 10 and 13, and the poor outcome group displayed a significant increase in LDI scores between ages 7 and 10. Rules for predicting increased risk for poor outcome status were evaluated, with results suggesting that the LDI may best serve as a “rule in” sign for increased risk of poor outcome.