Validity of WAIS-III short forms for patients with Alzheimer's disease and Parkinson's disease

Background: The Chinese version of the Wechsler Adult Intelligence Scale—Third Edition (WAIS-III) is the basic measure in clinical neuropsychological evaluations in Taiwan. Abbreviation of the WAIS-III is necessary due to clinical constraints, particularly in assessing patients with Alzheimer’s disease (AD) and Parkinson’s disease (PD). However, various tetrad combinations have not yet been comprehensively examined in patients with AD and PD in Taiwan.
Objective: To compare applications of all available factor-based tetrad combinations based upon linear equating and prorating procedures for IQ estimations in patients with AD and PD.
Methods: All tetrads were selected from one subtest of each WAIS-III index.
Administration time and psychometric properties including reliability and validity were investigated in all combinations of factor-based tetrads based upon the linear equating and prorating procedures.
Results: The two procedures could generate reasonable estimations though half of the estimations showed inflated variance in the clinical sample. In both patient groups, tetrads involving the Similarities, Block Design, and Symbol Search showed poorer estimation accuracy. The tetrad of Information-Matrix Reasoning-Arithmetic-Digit Symbol Substitution and Information-Picture Completion-Arithmetic-Digit Symbol Substitution were applicable to both patient groups. In addition, the tetrads of Information-Matrix Reasoning-Digit Span-Digit-Symbol Substitution, Vocabulary-Matrix Reasoning-Arithmetic-Digit Symbol Substitution, Vocabulary-Picture Completion-Arithmetic-Digit Symbol Substitution, Vocabulary-Picture Completion-Digit Span-Digit Symbol Substitution for patients with PD are also feasible.
Conclusion: Both the linear equating and the prorating procedures could generate reasonable IQ estimations when applied to AD and PD patients. These proposed tetrads for screening purposes and interpreting the results with further neurocognitive evaluations is recommended.