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.
SIB: The SIB contains 51 questions which take a total of about 20 min to administer, and the possible scores range from 0 to 100. The SIB is divided into 9 subscales, viz. social interaction skills (score 0-6), memory (score 0-14), orientation (score 0-6), language (score 0-46), attention (score 0-6), praxis (score 0-8), visuospatial ability (score 0-8), con- struction (score 0-4) and orienting to name (score 0-2), each of which yields individual scores. There is no cut-off score for normal subjects as the test is only intended to be used with patients known to be severely impaired. However, it is possi- ble to grade the severity of impairment by rating those who score less than 63 on the SIB (corresponding approximately to less than 4 on the MMSE).