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Evaluation of an 8-item Severe Impairment Battery (SIB-8) vs. the full SIB in moderate to severe Alzheimer's disease patients participating in a donepezil study

Authors


  • Disclosures FAS: Has no financial interests to report; has served on a Data Safety Monitoring Committee for Pfizer for which the University of Kentucky received reimbursement (< $4,000). JS: Currently receives royalties from the original SIB on which this reduced scale is based; Has been paid as a consultant to Eisai Inc./Pfizer Inc. SHF: Has served as a paid scientific consultant to Pfizer related to donepezil and to several investigational compounds ( < $10,000 per year; there was no payment for participation in this article). His institution has received grant/contract support from Pfizer for the conduct of clinical trials for dementia and to support educational programmes. He has also served as a scientific consultant to other companies marketing, developing or contributing to the development of drugs for cognition, including Accera, Baxter, Bristol-Myers Squibb, Eisai, Elan, Eli Lilly, Janssen AI, MedAvante, Merck, Merz, Neuronix, Novartis, Takeda and United Biosource; and his institution has received grant/contract support for clinical trials from Baxter, Bristol Myers-Squibb, Eisai, Eli Lilly, Janssen AI, Merck and Roche. He also has stock options from Accera, Intellect Neurosciences, MedAvante, and Neuronix, and stock from Lexicon. JM: Employee of Pfizer Inc. YS: Former employee of Eisai Inc.

Correspondence to:

Frederick A. Schmitt,

Departments of Neurology, Psychiatry, Behavioral Science, and Psychology, Sanders-Brown Center on Aging/Alzheimer's Disease Center, Room 312, 800 South Limestone Street, Lexington, KY 40536-0230, USA

Tel.: + 859 257-1412

Fax: + 859 323-2866

Email: fascom@uky.edu

Summary

Aim

The Severe Impairment Battery (SIB), a reliable cognitive measure for evaluating treatment response in advanced Alzheimer's disease (AD), takes approximately 20 min to administer. A recently derived 8-item version of the SIB – the SIB-8 – which takes about 3 min to administer, may represent a more convenient tool for use in clinical practice. The current analyses further explored the SIB-8 scale with respect to its validity and sensitivity.

Methods

A post hoc analysis was performed using data from a 24-week trial of donepezil 23 mg/day and 10 mg/day in > 1400 patients with moderate to severe AD [baseline Mini-Mental State Examination (MMSE) score 0–20]. Treatment effects on cognition (patterns of score change) were assessed using the full SIB and SIB-8 in the total study population and subgroups based on concomitant memantine use and baseline MMSE. Internal consistency/agreement and correlations between the SIB and SIB-8 and other clinical end points were evaluated.

Results

Assessment of score changes from baseline to week 24 with donepezil (23 or 10 mg/day) demonstrated comparable patterns of change when using the SIB-8 and the full SIB, despite inherent differences in the total score ranges for the two scales. Internal consistency/agreement between the full SIB and SIB-8 was good (Cronbach's alphas: 0.77–0.95). SIB-8 scores reliably correlated with SIB total scores (r = 0.859, baseline; r = 0.900, week 24; p < 0.0001), as well as MMSE scores (r = 0.7163, baseline; r = 0.7963, week 24; p < 0.0001). Scores on both SIB scales were moderately associated with functional measures at baseline and week 24.

Conclusions

In this post hoc analysis, similar treatment effects were measured by the full SIB and the SIB-8. Very good internal consistency/agreement and strong correlations between the SIB and the more rapid and convenient SIB-8 indicate that the SIB-8 may be a useful and efficient clinical proxy for the full SIB in evaluating treatment response in patients with advanced AD.

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