Escalante Agustín, Haas Roy W, del Rincón Inmaculada
Division of Rheumatology and Clinical Immunology, Department of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Arthritis Res Ther. 2004;6(4):R315-25. doi: 10.1186/ar1188. Epub 2004 May 21.
Outcome assessment in patients with rheumatoid arthritis (RA) includes measurement of physical function. We derived a scale to quantify global physical function in RA, using three performance-based rheumatology function tests (RFTs). We measured grip strength, walking velocity, and shirt button speed in consecutive RA patients attending scheduled appointments at six rheumatology clinics, repeating these measurements after a median interval of 1 year. We extracted the underlying latent variable using principal component factor analysis. We used the Bayesian information criterion to assess the global physical function scale's cross-sectional fit to criterion standards. The criteria were joint tenderness, swelling, and deformity, pain, physical disability, current work status, and vital status at 6 years after study enrolment. We computed Guyatt's responsiveness statistic for improvement according to the American College of Rheumatology (ACR) definition. Baseline functional performance data were available for 777 patients, and follow-up data were available for 681. Mean +/- standard deviation for each RFT at baseline were: grip strength, 14 +/- 10 kg; walking velocity, 194 +/- 82 ft/min; and shirt button speed, 7.1 +/- 3.8 buttons/min. Grip strength and walking velocity departed significantly from normality. The three RFTs loaded strongly on a single factor that explained >or=70% of their combined variance. We rescaled the factor to vary from 0 to 100. Its mean +/- standard deviation was 41 +/- 20, with a normal distribution. The new global scale had a stronger fit than the primary RFT to most of the criterion standards. It correlated more strongly with physical disability at follow-up and was more responsive to improvement defined according to the ACR20 and ACR50 definitions. We conclude that a performance-based physical function scale extracted from three RFTs has acceptable distributional and measurement properties and is responsive to clinically meaningful change. It provides a parsimonious scale to measure global physical function in RA.
类风湿关节炎（RA）患者的结局评估包括身体功能的测量。我们使用三项基于表现的风湿病功能测试（RFT）得出了一个量表，用于量化RA患者的整体身体功能。我们在六家风湿病诊所对连续就诊的RA患者测量了握力、步行速度和扣衬衫纽扣速度，在中位间隔1年后重复这些测量。我们使用主成分因子分析提取潜在变量。我们使用贝叶斯信息准则评估整体身体功能量表与标准的横断面拟合度。标准包括关节压痛、肿胀和畸形、疼痛、身体残疾、当前工作状态以及入组研究6年后的生命状态。我们根据美国风湿病学会（ACR）的定义计算了Guyatt反应性统计量以评估改善情况。777例患者有基线功能表现数据，681例有随访数据。每项RFT在基线时的平均±标准差分别为：握力，14±10千克；步行速度，194±82英尺/分钟；扣衬衫纽扣速度，7.1±3.8颗/分钟。握力和步行速度显著偏离正态分布。三项RFT在一个单一因子上有很强的负荷，该因子解释了其组合方差的≥70%。我们将该因子重新标度为从0到100。其平均±标准差为41±20，呈正态分布。新的整体量表比主要RFT与大多数标准的拟合度更强。它与随访时的身体残疾相关性更强，并且对根据ACR20和ACR50定义的改善更具反应性。我们得出结论，从三项RFT中提取的基于表现的身体功能量表具有可接受的分布和测量特性，并且对临床有意义的变化有反应。它为测量RA患者的整体身体功能提供了一个简洁的量表。
