Supplementary Material for: Evaluating Residual Cognition in Advanced Cognitive Impairment: The Residual Cognition Assessment

<b><i>Background:</i></b> In nursing homes, most of the patients with dementia are affected by severe cognitive disorder. Care interventions follow an accurate and recurring multidimensional assessment, including cognitive status. There is still a need to develop new performance-based scales for moderate-to-advanced dementia. <b><i>Objectives:</i></b> The development of the Residual Cognition Assessment (RCA) responds to the need to create new scales for global cognitive screening in advanced dementia, with some peculiar features: performance based, brief (&lt;5 m), available without specific training, and suitable for nonverbal patients with minimal distress. <b><i>Methods:</i></b> Two raters have administered the RCA and the Severe Impairment Battery-short version (SIB-S) to 84 participants with MMSE = 0. After 2–3 weeks, the same sample has been retested. The RCA has been also administered to 40 participants with MMSE 1–10 for a comparison. <b><i>Results:</i></b> The RCA has exhibited excellent values for test-retest reliability (intraclass correlation [ICC] = 0.956) as well as for inter-rater reliability (ICC = 0.997). The concurrent validity analyzes have shown strong correlations between the RCA and the SIB-S with ρ = 0.807 (<i>p</i> &lt; 0.01), and the RCA and the Clinical Dementia Rating (CDR) with ρ = −0.663 (<i>p</i> &lt; 0.01). Moderate correlation has been found between the RCA and the Functional Assessment Staging Scale with ρ = −0.435 (<i>p</i> &lt; 0.01). The instrument has showed high internal reliability, too (total: <i>α</i> = 0.899). The RCA has low floor effect (2%) with respect to the SIB-S (58%) but shows ceiling effect in the MMSE 1–10 sample (50%). The ROC curve analyses demonstrate that the RCA is acceptably able to discriminate between subjects with CDR 4/5 with an AUC of 0.92. Exploratory factor analysis shows 3 factors, defined as three major degrees of cognitive performance in advanced dementia, indeed hierarchically structured in three possible levels of decline. <b><i>Conclusions:</i></b> The RCA has showed excellent validity and reliability as well as good sensitivity to identify advanced cognitive impairment in dementia, without floor effect. The RCA seems complementary to the MMSE, so advisable when the latter reaches 0. Administration and scoring are simple, and only few minutes are required to assess the patient. The RCA can discriminate at least 3 different major stages in advanced dementias: severe, profound, and late.

**背景：** 养老机构中，多数痴呆患者存在重度认知功能障碍。临床护理干预需依托精准且可重复的多维度评估体系，其中包含认知状态评估。目前仍需针对中重度至晚期痴呆开发新型基于行为表现的评估量表。
**研究目的：** 残余认知评估量表（Residual Cognition Assessment, RCA）的开发，正是为了满足晚期痴呆患者整体认知筛查的新型量表开发需求，该量表具备以下独特特性：基于行为表现、耗时短（<5分钟）、无需专项培训即可使用，且可用于非语言沟通患者，对患者造成的心理负担极小。
**研究方法：** 2名评定者对84例简易精神状态检查表（Mini-Mental State Examination, MMSE）得分为0的受试者施测了RCA与严重损害量表简版（Severe Impairment Battery-short version, SIB-S）；于2~3周后，对同一受试队列进行重测。同时对40例MMSE得分1~10分的受试者施测RCA以开展对照分析。
**研究结果：** RCA展现出优异的重测信度（组内相关系数[ICC]=0.956）与评定者间信度（ICC=0.997）。同时效度分析显示，RCA与SIB-S呈强相关（ρ=0.807，*p*<0.01），与临床痴呆评定量表（Clinical Dementia Rating, CDR）亦呈强相关（ρ=-0.663，*p*<0.01）；RCA与功能评估分期量表（Functional Assessment Staging Scale）呈中等程度相关（ρ=-0.435，*p*<0.01）。该量表亦具备较高的内部一致性信度（总量表α=0.899）。相较于SIB-S的58%地板效应，RCA的地板效应仅为2%；但在MMSE得分1~10分的受试队列中，RCA存在50%的天花板效应。受试者工作特征曲线（Receiver Operating Characteristic, ROC）分析显示，RCA可较好地区分CDR 4/5级的受试者，曲线下面积（Area Under Curve, AUC）为0.92。探索性因子分析提取出3个因子，对应晚期痴呆患者认知表现的3个主要层级，该因子结构按认知衰退程度可划分为3个递进水平。
**研究结论：** RCA具备优异的效度与信度，且可灵敏识别痴呆患者的晚期认知功能障碍，且无地板效应。RCA可作为MMSE的补充评估工具，在MMSE得分为0时推荐使用该量表。RCA的施测与计分流程简便，仅需数分钟即可完成患者评估。RCA可至少区分晚期痴呆的3个主要阶段：重度、极重度及终末期痴呆。