A clinical bulbar assessment scale (CBAS) for amyotrophic lateral sclerosis.

Abstract

Comprehensive and valid bulbar assessment scales for use within amyotrophic lateral sclerosis (ALS) clinics are critically needed. The aims of this study are to develop the Clinical Bulbar Assessment Scale (CBAS) and complete preliminary validation. The authors selected CBAS items from among the literature and expert opinion, and content validity ratio (CVR) was calculated. Following consent, the CBAS was administered to a pilot sample of English-speaking adults with El Escorial defined ALS (N=54) from a multidisciplinary clinic, characterizing speech, swallowing, and extrabulbar features. Criterion validity was assessed by correlating CBAS scores with commonly used ALS scales, and internal consistency reliability was obtained. Expert raters reported strong agreement for the CBAS items (CVR=1.00; 100% agreement). CBAS scores yielded a moderate, significant, negative correlation with ALS Functional Rating Scale-Revised (ALSFRS-R) total scores (r=-0.652, p < .001), and a strong, significant, negative correlation with ALSFRS-R bulbar subscale scores (r=-0.795, p < .001). There was a strong, significant, positive correlation with Center for Neurologic Studies Bulbar Function Scale (CNS-BFS) scores (r=0.819, p < .001). CBAS scores were significantly higher for bulbar onset (mean=38.9% of total possible points, SD=22.6) than spinal onset (mean=18.7%, SD=15.8; p=.004). Internal consistency reliability (Cronbach's alpha) values were: (a) total CBAS, α=0.889; (b) Speech subscale, α=0.903; and (c) Swallowing subscale, α=0.801. The CBAS represents a novel means of standardized bulbar data collection using measures of speech, swallowing, respiratory, and cognitive-linguistic skills. Preliminary evidence suggests the CBAS is a valid, reliable scale for clinical assessment of bulbar dysfunction.