Karstoft Karen-Inge, Nielsen Anni B S, Nielsen Tine
Research and Knowledge Centre, The Danish Veteran Centre, Ringsted, Denmark.
The Research Unit and Section of General Practice, Institute of Public Health, University of Copenhagen, Copenhagen, Denmark.
Eur J Psychotraumatol. 2017 May 22;8(1):1326798. doi: 10.1080/20008198.2017.1326798. eCollection 2017.
: Depression is a common psychopathological outcome following military deployment. Previous studies have reported differing rates of post-deployment depression, indicating that the toll of war differs across missions. However, it is unclear to what degree the varying prevalence is due methodological differences. Studies comparing rates of depression across cohorts using the same methodology and ensuring measurement invariance are rare, leaving us with limited knowledge on the actual depression prevalence variance across missions. : Applying Rasch models (RM), we aim to validate a measure of depression distributed to all personnel deployed with the Danish Defense since 1998. The main focus was establishing a sufficient sum score and measurement invariance relative to deployment cohort. : Two cohorts of the International Security Assistance Force (ISAF) deployed to Afghanistan in 2009 (ISAF7, = 265) and 2013 (ISAF15, = 271) were included. Participants filled out a questionnaire concerning their Psychological Reactions to International Missions (PRIM) approximately seven months after home-coming. The questionnaire included a 10-item scale of depression symptoms (PRIM-Depression). The validity of the PRIM-Depression was tested using RM with specific focus on differential item functioning (DIF) across the two cohorts. : The PRIM-Depression scale displayed excellent overall consistency and showed no problems with monotonicity or homogeneity. However, the full PRIM-Depression scale did not fit a pure RM. We therefore tested the fit of items to a graphical log-linear RM and found evidence of DIF for two items relative to cohort. We proceeded without these two items and tested the resulting 8-item version which fitted a pure RM without DIF on any of the exogenous variables. : Our results suggest that the 10-item PRIM-Depression scale should be used to compare cohorts only with appropriate score equation. The 8-item version provides a sufficient statistic and can as such be applied using the raw score.
抑郁症是军事部署后常见的精神病理结果。先前的研究报告了部署后抑郁症的不同发生率，表明战争的影响在不同任务中有所不同。然而，尚不清楚不同的患病率在多大程度上是由于方法学差异造成的。使用相同方法并确保测量不变性来比较不同队列中抑郁症发生率的研究很少，这使得我们对不同任务中实际抑郁症患病率差异的了解有限。
应用拉施模型（RM），我们旨在验证自1998年以来分发给所有丹麦国防军部署人员的抑郁症测量方法。主要重点是建立一个足够的总分，并相对于部署队列建立测量不变性。
纳入了2009年（ISAF7，n = 265）和2013年（ISAF15，n = 271）部署到阿富汗的国际安全援助部队（ISAF）的两个队列。参与者在回国后约七个月填写了一份关于他们对国际任务的心理反应（PRIM）的问卷。该问卷包括一个10项的抑郁症状量表（PRIM-抑郁症）。使用RM测试了PRIM-抑郁症的有效性，特别关注两个队列之间的差异项目功能（DIF）。
PRIM-抑郁症量表显示出极好的总体一致性，并且在单调性或同质性方面没有问题。然而，完整的PRIM-抑郁症量表并不符合纯RM。因此，我们测试了项目与图形对数线性RM的拟合情况，发现有两个项目相对于队列存在DIF的证据。我们去掉这两个项目后继续进行测试，测试了由此产生的8项版本，该版本符合纯RM，且在外生变量上没有DIF。
我们的结果表明，10项PRIM-抑郁症量表仅应使用适当的得分方程来比较队列。8项版本提供了一个足够的统计量，因此可以使用原始分数进行应用。
