Identifying disability score differences in people with schizophrenia according to sociodemographic and clinical variables can help design better rehabilitation or care programs, but in order to compare the scores, it is necessary to confirm the measurement invariance. This study analyses differential item functioning (DIF) in the WHODAS 2.0 (WHO Disability Assessment Schedule) by applying two procedures based on Rasch trees (TREE-PCM and PCM-IFT). A total of 352 patients with schizophrenia spectrum disorder aged between 18 and 55 years took part. Sociodemographic (gender, age, marital status, and education) and clinical (depressive symptomatology, and presence of positive and negative symptoms) covariates were analysed in each of the WHODAS 2.0 domains. The TREE-PCM did not detect DIF, while with PCM-IFT an item with DIF was detected for the age variable. Although the findings suggest that only one item presents DIF, this refers to important issues when assessing functioning in patients with schizophrenia and should be reviewed.

根据社会人口学和临床变量识别精神分裂症患者的残疾评分差异有助于设计更好的康复或护理计划，但为了比较评分，有必要确认测量的不变性。本研究通过应用两个基于 Rasch 树（TREE-PCM 和 PCM-IFT）的程序来分析 WHODAS 2.0（WHO 残疾评估表）中的差异项目功能 (DIF)。共有 352 名年龄在 18 至 55 岁之间的精神分裂症谱系障碍患者参加。在每个 WHODAS 2.0 域中分析了社会人口学（性别、年龄、婚姻状况和教育）和临床（抑郁症状，以及存在阳性和阴性症状）协变量。TREE-PCM 没有检测到 DIF，而使用 PCM-IFT 时，为年龄变量检测到具有 DIF 的项目。尽管研究结果表明只有一个项目呈现 DIF，但这指的是评估精神分裂症患者功能时的重要问题，应进行审查。