Practice effect and test-retest reliability of the Wechsler Memory Scale-Fourth Edition in people with dementia.

BACKGROUND: The Wechsler Memory Scale-Fourth Edition (WMS-IV) has been widely used to assess memory function in people with dementia. The older adult battery of the WMS-IV includes four indices and seven subtests. The aims of this study were to examine the practice effect and test-retest reliability and calculate the reliable change index modified for practice (RCIp) for the indices and subtests of the older adult battery of the WMS-IV for people with dementia. METHODS: Fifty-six participants completed the WMS-IV twice, two weeks apart. The practice effect was investigated using effect size (Cohen's d) and bootstrapping mixed design analysis of variance while considering the severity of dementia. The test-retest reliability was estimated using intraclass correlation coefficient (ICC). RESULTS: The results showed non-significant practice effects with Cohen's d < 0.20 in different severities of dementia on two indices and five subtests. The ICC values of these indices and subtests were 0.82-0.85 and 0.57-1.00, respectively. The other two indices (i.e., auditory memory and immediate memory) and two subtests (i.e., logical memory delayed recall and visual reproduction immediate recall) demonstrated small to moderate practice effect (d = 0.46-0.74) for people with mild severity of dementia. CONCLUSION: On the whole, the WMS-IV has no to moderate practice effects and moderate to excellent test-retest reliability in people with dementia. The values of the RCIp with 95% confidence interval for the indices and subtests were provided in this study, which are useful to clinicians and researchers for interpreting the real score change in persons with dementia. The two indices (i.e., auditory memory and immediate memory) and two subtests (i.e., logical memory delayed recall and visual reproduction immediate recall) with noticeable practice effect should be used with caution when assessing memory function repeatedly in people with mild severity of dementia.

Measurement Equivalence between the Original and Estimated Mini-Mental State Examination in People with Dementia.

BACKGROUND: The Cognitive Abilities Screening Instrument (CASI) is increasingly used to assess general cognitive function in people with dementia. The Mini-Mental State Examination (MMSE) score can be converted from the CASI (i.e., the estimated MMSE). Recognizing that measurement equivalence is critical to meaningfully representing one with the other, we aimed to determine whether the estimated MMSE score obtained from the CASI was equivalent to the original MMSE in people with dementia. METHODS: We obtained 110 data points for the MMSE and CASI scores in people with dementia. The intraclass correlation coefficient (ICC), Pearson's r, percent of standard error of measurement (SEM%), paired t-test, and effect size (Cohen's d) were used to investigate the equivalence. RESULTS: To examine the equivalence between the original and estimated MMSE score, the ICC and Pearson's r of the total score and six domains were 0.62-0.95 and 0.62-0.96, respectively. The SEM% of the total score and six domains were 0.6-8.9%. The paired t-test results showed a significant difference (p < 0.05) between the total score and the three domains. The Cohen's d of the total score and six domains were 0.06-0.27. CONCLUSIONS: The estimated MMSE score was found to have moderate to excellent equivalence to the original MMSE score. The three domains (i.e., registration, attention and calculation, and visual-constructional ability) with moderate equivalence should be used cautiously to interchange with the original MMSE in people with dementia.