[The five-word test in three age-groups of mild Alzheimer's disease (60, 70 and 80 year-old patients): Utility of the Total Score, Total Weighted Score, Learning Score and Memory Score]

Introduction: The five-word test (5WT) is a serial verbal memory test with semantic cuing. It is proposed to rapidly evaluate memory of aging people and has previously shown its sensitivity and its specificity in identifying patients with AD. It measures the efficacy of free and cued recalls during a procedure of immediate and delayed recalls.

Methods: The 5WT was compared in a group of 202 normal subjects and a group of 302 mild AD patients (MMS of 20 or more) aged from 60 to 92 years, in three age classes (60 years, 70 years, 80 years). Nine scores were measured (Total Score, Total Weighted Score, Free Immediate Recall, Learning Score=total of Immediate Recalls, Free Delayed Recall, Memory Score=total of Delayed Recalls, Forgetting Rate, Percentage of Immediate Cuing, Percentage of Delayed Cuing) as well as the presence of intrusions. For each age class, Receiver Operating Characteristic curves determined the most significant cut-off scores.

Results: For each score of the 5WT, AD patients differed significantly from controls. The cut-off scores were not the same according to age. For the Total Score, the cut-off scores were 10 (60 years), 9 (70 years) and 8 (80 years), whereas the cut-off scores of the Total Weighted Score were 17 (60 years), 16 (70 years) and 14 (80 years). As suggested by Cowppli-Bony et al. (2005), the Total Weighted Score (which gives a higher coefficient to free recalls) was better than the Total Score for discriminating mild AD. The 5WT is useful to discriminate normal controls and mild AD patients. Normal aged subjects displayed good encoding, efficient stocking and consolidation (few forgetting, efficient cued recall), intrusions were rare. Mild AD patients were characterized by weak encoding of words and severe deficit for stocking and consolidation (important forgetting, impaired cued recall), they made numerous intrusions. This psychometric profile is characteristic of the amnestic hippocampal syndrome found in AD.

Conclusion: The 5WT is a simple and reliable test for investigating memory in elderly people above 60 years old. According to age, different cut-offs are needed for the Total Score and the Total Weighted Score, the latter appearing more discriminating than the Total Score for the diagnosis of mild AD. It is also interesting to evaluate the presence of intrusions. Lastly, it is important to consider the forgetting rate (between Learning and Memory Scores) in order to confirm the presence of a hippocampal amnesia.