Mowinckel Petter, Hagen Kåre B, Heiberg Turid, Kvien Tore K
National Resource Centre for Rehabilitation in Rheumatology, Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway.
J Clin Epidemiol. 2008 Sep;61(9):940-4. doi: 10.1016/j.jclinepi.2007.12.004. Epub 2008 Jun 6.
To investigate whether repeated measures in patients with rheumatoid arthritis will reduce the between subject variation and if so, to determine the optimal number of measures to effectively reduce the number of participants required in controlled clinical trials.
A prospective observational study. Thirty-eight rheumatoid arthritis patients with a stable disease reported level of joint pain, fatigue and patient global assessment of disease activity on VAS scales as well as the Rheumatoid Arthritis Disease Activity Index (RADAI) daily during a total of 42 days.
In all measures, the variation within each individual was substantial over a 42-day period. By increasing the number of measurements from one to five, the standard deviation (SD) decreased from 5.5% (RADAI score) to 11% (Pain VAS) resulting in a reduction in the number of patients needed in a clinical trial from 11% to 22%, respectively. When we used from 6 to 42 individual measurements, the decrease continued but the reduction was of a smaller magnitude.
The use of up to five repeated measurements per patient will decrease the number of patients required in a two armed clinical trial by as much as 22%.
研究类风湿关节炎患者的重复测量是否会减少个体间差异，若能减少，则确定有效减少对照临床试验所需参与者数量的最佳测量次数。
一项前瞻性观察性研究。38例病情稳定的类风湿关节炎患者在总共42天的时间里，每天报告关节疼痛程度、疲劳程度以及用视觉模拟量表（VAS）对疾病活动进行的患者整体评估，同时报告类风湿关节炎疾病活动指数（RADAI）。
在所有测量中，每个个体在42天内的差异都很大。通过将测量次数从1次增加到5次，标准差（SD）从5.5%（RADAI评分）降至11%（疼痛VAS），这使得临床试验所需患者数量分别从11%降至22%。当我们使用6至42次个体测量时，标准差继续下降，但下降幅度较小。
每位患者最多进行5次重复测量，将使双臂临床试验所需患者数量减少多达22%。
