Wechsler Adult Intelligence Scale, 3rd Edition (WAIS-III): Usefulness in the Early Detection of Alzheimer's Disease

We examined Alzheimer's disease (AD) patients using a Japanese version of the Wechsler Adult Intelligence Scale, 3rd Edition (JWAIS-III) to clarify i) the significance of expansion of the indicated age range, ii) the characteristics of cognitive impairment in AD patients and iii) the efficacy of th neuropsychological assessment for the early detection of AD using the Digit Symbol subtest, which involves attention and episodic memory, and the Pairing supplementary test, which relates to digit symbol-incidental learning. The JWAIS-III was given to 43 AD patients (12 males and 31. females; mean age, 80.9 +/- 6.3 years, who fulfilled the diagnostic criteria for AD on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) and the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association. Severity of dementia of the patients was classified according to Functional Assessment Staging (F) as follows: 9 patients in F3 (borderline), 15 in F4 (mild AD), 12 in F5 (moderate AD), 7 in F6 (somewhat severe AD) and none in F7 (severe AD). i) Mean intelligence quotients (IQs) were: Full Scale IQ 84.3 +/- 14.0, Verbal IQ 84.6 +/- 12.5 and Performance IQ 86.9 +/- 15.5. Comparison of IQs and subtest scores of the patients aged 75 years or older assessed by standard scores for 70 to 74 years of age, which is the upper limit of the indicated age range on the WAIS-R (the previous version of the WAIS-III), with those assessed by the standard scores for the appropriate age revealed that the former were significantly lower in IQ and all subtest scores. ii) Significant differences were noted among the severities of dementia in the scores of 7 subtests for Similarities, Comprehension, Arithmetic, Digit Span, Letter-Number Sequencing, Digit Symbol and Symbol Search. iii) When both the Digit Symbol subtest scores of 7 points or more and the Digit Sumbol-Pairing supplementary test scores exceeding 10% of the cumulative percentile were regarded as normal, 11 of 15 (73.3%) patients in F4 (mild AD) could be detected. These findings suggest that i) expansion of the indicated age range in the WAIS-III allows a more valid assessment of cognitive function in AD patients, ii) a marked decline in abstract thinking and verbal problem-solving ability and relative preservation of Perceptual organization are characteristics of cognitive impairment in AD patients and iii) a combination of the Digit Symbol subtest with the Pairing supplementary test is useful for the early detection of AD.