The psychometric process used to establish a relationship between the scores of two (or more) instruments is generically referred to as linking. When two instruments with the same content and statistical test specifications are linked, these instruments are said to be equated. Linking and equating procedures have long been used for practical benefit in educational testing. In recent years, health outcome researchers have increasingly applied linking techniques to patient-reported outcome (PRO) data. However, these applications have some noteworthy purposes and associated methodological questions. Purposes for linking health outcomes include the harmonization of data across studies or settings (enabling increased power in hypothesis testing), the aggregation of summed score data by means of score crosswalk tables, and score conversion in clinical settings where new instruments are introduced, but an interpretable connection to historical data is needed. When two PRO instruments are linked, assumptions for equating are typically not met and the extent to which those assumptions are violated becomes a decision point around how (and whether) to proceed with linking. We demonstrate multiple linking procedures—equipercentile, unidimensional IRT calibration, and calibrated projection—with the Patient-Reported Outcomes Measurement Information System Depression bank and the Patient Health Questionnaire-9. We validate this link across two samples and simulate different instrument correlation levels to provide guidance around which linking method is preferred. Finally, we discuss some remaining issues and directions for psychometric research in linking PRO instruments.

用于在两个（或多个）工具的分数之间建立关系的心理测量过程通常称为链接。当具有相同内容和统计测试规范的两个仪器被链接时，这些仪器被称为等同。长期以来，链接和等同程序一直用于教育测试中的实际利益。近年来，健康结果研究人员越来越多地将链接技术应用于患者报告的结果 (PRO) 数据。然而，这些应用程序有一些值得注意的目的和相关的方法论问题。将健康结果联系起来的目的包括跨研究或设置协调数据（提高假设检验的能力），通过分数交叉表汇总总分数据，以及引入新仪器的临床设置中的分数转换，但需要与历史数据的可解释联系。当两台 PRO 乐器连接时，通常不满足等同假设，并且违反这些假设的程度成为关于如何（以及是否）进行链接的决策点。我们展示了多个链接程序——等百分位、一维 IRT 校准和校准投影——与患者报告的结果测量信息系统抑郁库和患者​​健康问卷 9。我们验证了两个样本之间的这种联系，并模拟了不同的仪器相关水平，以提供关于首选哪种链接方法的指导。最后，我们讨论了连接 PRO 仪器的心理测量研究的一些遗留问题和方向。和校准预测——使用患者报告结果测量信息系统抑郁库和患者​​健康问卷 9。我们验证了两个样本之间的这种联系，并模拟了不同的仪器相关水平，以提供关于首选哪种链接方法的指导。最后，我们讨论了连接 PRO 仪器的心理测量研究的一些遗留问题和方向。和校准预测——使用患者报告结果测量信息系统抑郁库和患者​​健康问卷 9。我们验证了两个样本之间的这种联系，并模拟了不同的仪器相关水平，以提供关于首选哪种链接方法的指导。最后，我们讨论了连接 PRO 仪器的心理测量研究的一些遗留问题和方向。