Severe Impairment Battery Language scale: a language-assessment tool for Alzheimer's disease patients.

ABSTRACT

BACKGROUND: Communication problems are common in Alzheimer's disease (AD) patients, but instruments to assess these symptoms are limited. Our objective was to create a new scale, based on the language subscale of the Severe Impairment Battery (SIB), as a sensitive and reliable measurement of treatment effects on language performance. METHODS: All 24 items of the SIB language subscale were chosen for analysis. Baseline scores of 1320 moderate-to-severe patients (Mini-Mental State Examination [MMSE] score, <15), from a combined AD database of four Memantine clinical trials (Study Codes IE-2101, MEM-MD-01, MEM-MD-02, and MRZ-9605), were used for item reduction according to a standard principal components factor analysis. All items with loadings >0.5 on the identified factors were selected for inclusion in the new language scale. Correlations with existing AD scales were examined. RESULTS: The analysis indicated six factors, with 21 of 24 items showing loadings >0.5. The resulting 21-item SIB Language (SIB-L) scale exhibited high internal consistency (Cronbach's alpha = 0.809). The maximal SIB-L score was 41 points, with a measurement error of 3.7 points. The stratification of baseline SIB-L scores (mean, 31.7; SD, 8.4) by MMSE scores (mean, 9.7; SD, 3.3) showed a high variance in SIB-L scores. This confirms that patients with a low MMSE score can possess preserved language abilities. The SIB-L scale did not exhibit substantial floor-and-ceiling effects. CONCLUSIONS: The new SIB-L is a fast (<15 minutes) and easily administered scale with favorable psychometric characteristics for assessing language impairment and treatment effects on the language performance of patients with moderate to severe AD.