Natl Health Stat Report. 2021 Jun(156):1-15.
Background-The National Cancer Institute (NCI) Joinpoint regression software is a widely used software program for evaluating trends. In addition to producing model estimates for trend models, this software can search for changes in slope along the trend line. One component of the software, which tests whether line segment slopes are zero, is different from the usual t-test of zero slope that is used in linear models. This report will demonstrate this Joinpoint software procedure through replication using the SAS Institute's statistical software (that is, SAS) and discuss the implications of the different assumptions used by Joinpoint and a typical SAS model for the test of zero slope. Methods-First, Joinpoint's procedure for testing a zero slope is compared with a typical test of zero slope using SAS, and the assumptions behind both approaches are evaluated. Second, the test from the Joinpoint software is replicated in SAS using its PROC REG procedure and additional SAS programming. Trend analyses of rates of drug overdose deaths involving fentanyl from the general population and among females are used as examples. Results-In the evaluation of the trend of drug overdose deaths for the total population, Joinpoint produces a similar result to the linear model test in SAS. For the female subgroup, however, Joinpoint and SAS produce differing results for the test of zero slope. The replication of the Joinpoint test of zero slope using SAS demonstrates that Joinpoint's procedure is based on fewer degrees of freedom, which results in a larger standard error estimate. Conclusion-The Joinpoint approach accounts for the fact that the joinpoints are estimated and thus leads to a more conservative hypothesis test, particularly when the number of points in a trend analysis is small.
背景-美国国家癌症研究所（NCI）Joinpoint 回归软件是一种广泛使用的评估趋势的软件程序。除了为趋势模型生成模型估计外，该软件还可以沿趋势线搜索斜率的变化。该软件的一个组件，用于测试线段斜率是否为零，与线性模型中常用的零斜率 t 检验不同。本报告将通过使用 SAS 研究所的统计软件（即 SAS）重复演示该 Joinpoint 软件程序，并讨论 Joinpoint 和典型 SAS 模型用于零斜率检验的不同假设的影响。
方法-首先，将 Joinpoint 测试零斜率的过程与 SAS 中典型的零斜率测试进行比较，并评估这两种方法背后的假设。其次，使用其 PROC REG 过程和其他 SAS 编程在 SAS 中复制 Joinpoint 软件中的测试。使用涉及芬太尼的一般人群和女性药物过量死亡率的趋势分析作为示例。
结果-在评估总体人群药物过量死亡趋势时，Joinpoint 产生的结果与 SAS 中的线性模型测试相似。然而，对于女性亚组，Joinpoint 和 SAS 对零斜率检验的结果不同。使用 SAS 复制 Joinpoint 零斜率检验表明，Joinpoint 的程序基于较少的自由度，这导致更大的标准误差估计。
结论-Joinpoint 方法考虑到了连接点的估计，因此导致更保守的假设检验，尤其是在趋势分析中的点数较少时。
