Diagnostic utility of the Learning Disability Index

The Learning Disability Index (LDI) is one of many diagnostic indicators proposed for the identification of students with learning disabilities that relies on patterns of performance on cognitive tests. The LDI is hypothesized to relate to students' specific neuropsychological deficits. The present study investigated the diagnostic utility of the LDI with the third edition of the Wechsler Intelligence Scale for Children by comparing students previously diagnosed with learning disabilities (n = 2,053) to students without learning disabilities (n = 2,200). Subsamples of youth with specific reading (n = 445) and math (n = 168) disabilities permitted further assessment of the efficacy of the LDI. Receiver operating characteristic (ROC) curves revealed that the LDI resulted in a correct diagnostic decision only 55% to 64% of the time. These results demonstrate that the LDI is not a valid diagnostic indicator of learning disabilities.