Rankin G, Stokes M
Royal Hospital for Neuro-disability, London, UK.
Clin Rehabil. 1998 Jun;12(3):187-99. doi: 10.1191/026921598672178340.
To provide a practical guide to appropriate statistical analysis of a reliability study using real-time ultrasound for measuring muscle size as an example.
Inter-rater and intra-rater (between-scans and between-days) reliability.
Ten normal subjects (five male) aged 22-58 years.
The cross-sectional area (CSA) of the anterior tibial muscle group was measured using real-time ultrasonography.
Intraclass correlation coefficients (ICCs) and the 95% confidence interval (CI) for the ICCs, and Bland and Altman method for assessing agreement, which includes calculation of the mean difference between measures (d), the 95% CI for d, the standard deviation of the differences (SDdiff), the 95% limits of agreement and a reliability coefficient.
Inter-rater reliability was high, ICC (3,1) was 0.92 with a 95% CI of 0.72 --> 0.98. There was reasonable agreement between measures on the Bland and Altman test, as d was -0.63 cm2, the 95% CI for d was -1.4 --> 0.14 cm2, the SDdiff was 1.08 cm2, the 95% limits of agreement -2.73 --> 1.53 cm2 and the reliability coefficient was 2.4. Between-scans repeatability was high, ICCs (1,1) were 0.94 and 0.93 with 95% CIs of 0.8 --> 0.99 and 0.75 --> 0.98, for days 1 and 2 respectively. Measures showed good agreement on the Bland and Altman test: d for day 1 was 0.15 cm2 and for day 2 it was -0.32 cm2, the 95% CIs for d were -0.51 --> 0.81 cm2 for day 1 and -0.98 --> 0.34 cm2 for day 2; SDdiff was 0.93 cm2 for both days, the 95% imits of agreement were -1.71 --> 2.01 cm2 for day 1 and -2.18 --> 1.54 cm2 for day 2; the reliability coefficient was 1.80 for day 1 and 1.88 for day 2. The between-days ICC (1,2) was 0.92 and the 95% CI 0.69 --> 0.98. The d was -0.98 cm2, the SDdiff was 1.25 cm2 with 95% limits of agreement of -3.48 --> 1.52 cm2 and the reliability coefficient 2.8. The 95% CI for d (-1.88 --> -0.08 cm2) and the distribution graph showed a bias towards a larger measurement on day 2.
The ICC and Bland and Altman tests are appropriate for analysis of reliability studies of similar design to that described, but neither test alone provides sufficient information and it is recommended that both are used.
以实时超声测量肌肉大小为例，提供一份关于可靠性研究的适当统计分析实用指南。
评估者间及评估者内（扫描间和日间）可靠性。
10名年龄在22至58岁之间的正常受试者（5名男性）。
使用实时超声测量胫前肌群的横截面积（CSA）。
组内相关系数（ICC）及其95%置信区间（CI），以及用于评估一致性的Bland和Altman方法，包括测量值之间的平均差异（d）计算、d的95% CI、差异标准差（SDdiff）、95%一致性界限和可靠性系数。
评估者间可靠性高，ICC（3,1）为0.92，95% CI为0.72至0.98。在Bland和Altman检验中测量值之间具有合理的一致性，d为-0.63平方厘米，d的95% CI为-1.4至0.14平方厘米，SDdiff为1.08平方厘米，95%一致性界限为-2.73至1.53平方厘米，可靠性系数为2.4。扫描间重复性高，第1天和第2天的ICC（1,1）分别为0.94和0.93，95% CI分别为0.8至0.99和0.75至0.98。在Bland和Altman检验中测量值显示出良好的一致性：第1天的d为0.15平方厘米，第2天为-0.32平方厘米，第1天d的95% CI为-0.51至0.81平方厘米，第2天为-0.98至0.34平方厘米；两天的SDdiff均为0.93平方厘米，第1天的95%一致性界限为-1.71至2.01平方厘米，第2天为-2.18至1.54平方厘米；第1天的可靠性系数为l.80，第2天为1.88。日间ICC（1,2）为0.92，95% CI为0.69至0.98。d为-0.98平方厘米，SDdiff为1.25平方厘米，95%一致性界限为-3.48至1.52平方厘米，可靠性系数为2.8。d的95% CI为（-1.88至-0.08平方厘米），分布图显示第2天测量值有偏大的偏差。
ICC以及Bland和Altman检验适用于分析与本文所述类似设计的可靠性研究，但单独使用任何一种检验都不能提供足够的信息，建议同时使用两者。
