University of Alabama at Birmingham, Department of Physical Therapy, Birmingham, Alabama, USA.
Kessler Foundation, West Orange, New Jersey, USA.
Phys Ther. 2021 Feb 4;101(2). doi: 10.1093/ptj/pzaa227.
There is evidence supporting the construct validity of Six-Spot Step Test (SSST) performance as a functional mobility measure in people with multiple sclerosis (MS); however, it is unknown if cognitive processing speed impairment confounds the construct validity of SSST performance in MS, as this test seemingly requires intact cognitive processing. The objective of this study was to examine the influence of cognitive processing speed impairment on the construct validity and precision of SSST performance as a functional mobility measure in MS.
Participants (N = 213) completed the SSST, timed 25-foot walk, 6-Minute Walk Test, Timed "Up and Go" Test, Multiple Sclerosis Walking Scale-12, device-measured steps per day, and Late-Life Function and Disability Inventory, Patient-Determined Disease Steps, and the Symbol-Digit Modalities Test as a cognitive processing speed measure. The overall sample was divided into subsamples with (n = 75) and without (n = 138) cognitive processing speed impairment based on normative Symbol-Digit Modalities Test data. Correlations between SSST performance with other mobility outcomes in the overall sample and cognitive processing speed impairment subsamples were examined and compared. SSST performance was compared relative to other mobility measures for differentiating MS walking function levels in people with and without cognitive processing speed impairment.
SSST performance was significantly and strongly correlated with most mobility outcomes in the overall sample and cognitive processing speed impairment subsamples. The magnitudes of correlations between SSST performance with most mobility outcomes were not statistically different among subsamples. Cognitive processing speed impairment did not diminish the relative precision of SSST performance for differentiating walking function levels.
The presence of cognitive processing speed impairment is not a source of invalidity or imprecision when interpreting SSST performance as a functional mobility measure among people with MS.
The SSST is a high-quality endpoint for inclusion in interventions targeting mobility in MS, regardless of cognitive processing speed status. This information is critical for rehabilitation research and clinical practice given that mobility and cognitive impairment are highly prevalent, co-occurring, and disabling in MS.
有证据支持六分点步测（SSST）作为多发性硬化症（MS）患者的功能性移动性测量指标的结构有效性；然而，目前尚不清楚认知处理速度受损是否会影响 SSST 作为 MS 功能性移动性测量指标的结构有效性，因为该测试似乎需要完整的认知处理能力。本研究的目的是检查认知处理速度受损对 SSST 作为 MS 功能性移动性测量指标的结构有效性和精密度的影响。
参与者（N=213）完成了 SSST、25 英尺步行计时、6 分钟步行测试、计时“起立和行走”测试、多发性硬化步行量表-12、设备测量的每日步数、晚年功能和残疾量表、患者确定的疾病步骤和符号数字模态测试作为认知处理速度的测量指标。根据符号数字模态测试的标准数据，将整个样本分为有认知处理速度受损（n=75）和无认知处理速度受损（n=138）的亚组。在整个样本和认知处理速度受损亚组中，检查和比较了 SSST 表现与其他移动性结果之间的相关性。比较了 SSST 表现与其他移动性指标在区分有和无认知处理速度受损者的 MS 步行功能水平方面的差异。
在整个样本和认知处理速度受损亚组中，SSST 表现与大多数移动性结果显著且呈强相关。SSST 表现与大多数移动性结果之间的相关性大小在亚组之间没有统计学差异。认知处理速度受损并未降低 SSST 表现区分步行功能水平的相对精度。
在多发性硬化症患者中，认知处理速度受损并不是解释 SSST 作为功能性移动性测量指标时无效或不精确的原因。
无论认知处理速度状况如何，SSST 都是多发性硬化症干预措施中纳入的高质量终点。鉴于多发性硬化症中移动性和认知障碍的高患病率、共同发生和致残性，这一信息对于康复研究和临床实践至关重要。
