Sensitivity and Test-Retest Reliability of the International Shopping List Test in Assessing Verbal Learning and Memory in Mild Alzheimer's Disease

Abstract

The International Shopping List Test (ISLT) was developed specifically to assess verbal list learning and memory in people from different language and cultural backgrounds. In this paper, we describe three studies that examined the sensitivity and reliability of the ISLT in assessing verbal list learning and memory impairment in English-speaking people with mild Alzheimer's disease (AD) and evaluated whether measures of retention-weighted recall (RWR) provided greater sensitivity and/or reliability relative to conventional list learning performance measures (e.g., free recall). In Study 1, we compared ISLT performance between patients with AD and matched controls and found that AD patients showed a large magnitude impairment on all ISLT performance measures (Cohen's d values >2). The RWR measure was more sensitive to detecting AD-related impairment than the free recall measure for Trial 1, although the most sensitive measures of the ISLT were free recall from Trial 3 and delayed recall. In Study 2, we compared RWR and free recall measures between 10- and 12-word versions of the ISLT, but found no difference between performance measures for the different list lengths. In Study 3, we evaluated test-retest reliabilities of the different outcome measures derived from the ISLT and found that measures of free recall had higher reliabilities than the RWR measures. Taken together, results of these studies suggest that measures of total free recall during learning trials and delayed recall from the 12-word version of the ISLT provide the greatest sensitivity to detecting verbal list learning and memory impairment in AD and that this task shows good test-retest reliability.