A psychometric comparison of DSM-IV and DSM-5 adapted scales for measuring PTSD in trauma-affected refugees

​1. Title: 

A psychometric comparison of DSM-IV and DSM-5 adapted scales for measuring PTSD in trauma-affected refugees 

2. Project period: 

January 2020 - December 2021 

3. Investigator(s): 

Erik Vindbjerg 

4. Supervisors and collaborative partners: 

Jessica Carlsson, Maja Bruhn Kristiansen 

5. Background 

For the diagnosis of PTSD, the recent transition to the DSM-5 and the upcoming transition to the ICD-11 implies a break with previous agreement between the two diagnostic systems, as well as a fragmentation of available measurement scales for PTSD. For measuring symptoms of PTSD, we may continue to use scales based on the previous diagnostic definitions — building on existing consensus — or news scale based on either the DSM-5 or ICD-11. The Harvard Trauma Questionnaire part four (HTQ) constitutes the de facto standard in measuring symptoms of PTSD with refugees and an update to the scale is pending, to bring it in line with DSM-5 definitions. This update mainly consists of adding more items to the Numbing cluster. Currently, however, there is little evidence that such an addition will bring improved validity to the scale. As the existing version of the HTQ has been subjected to extensive psychometric evaluation at the Competence Centre for Transcultural Psychiatry (CTP; Vindbjerg, Carlsson, Mortensen, Elklit, & Makransky, 2016; Vindbjerg et al., n.d.), this offers a solid reference for further analyses of an updated HTQ. By adding five symptoms to the existing HTQ, it is possible to do a comparative analysis of the existing and updated version. 

6. Aim/s 

To evaluate the added psychometric value of an DSM-5 modified HTQ over the original HTQ. The specific objective is to subject both scales to psychometric analysis, determining dimensional structure and potential cases of local dependence and differential item functioning. 

7. Methods 

7.1 Number of participants (N): 

200 

7.2 Population: 

Adult refugees and adult reunified family members of refugees undergoing psychiatric treatment for PTSD. 

7.3 Description of data and data collection 

Data will be collected as part of a larger randomized controlled trial at the CTP: "The effect of integrating cross-sectoral collaboration in psychosocial treatment of trauma-affected refugees; a randomised controlled trial". Responses are obtained as part of each patient’s second rating, at the time of transitioning to psychotherapy. The following translations of the HTQ will be used: Arabic, and Farsi. As no DSM-5 update to the HTQ is currently available, the additional DSM-5 items will be carried over from the PCL-5 (Blevins, Weathers, Davis, Witte, & Domino, 2015). While the PCL-5 uses five response categories, the items will be administered with the four response categories of the HTQ. Additionally, for this study, two of the items are divided into separate items covering distinct concepts that are compounded in the original PCL-5 items. This is intended to promote the understanding of each item as well as a separate psychometric analysis of each concept. The added items are listed below, with separated items followed by an alphabetic suffix: 

The included PCL-5 items are listed below, with separated items followed by an alphabetic suffix: 

  • PCL-5 item 14: Trouble experiencing positive feelings (for example, being unable to feel happiness or have loving feelings for people close to you)? 
  • PCL-5 item 9a: Having strong negative beliefs about yourself (for example, having thoughts such as: I am bad, there is something seriously wrong with me) 
  • PCL-5 item 9b: Having strong negative beliefs about other people (for example, no one can be trusted) 
  • PCL-5 item 9c: Having strong negative beliefs about the world (for example, the world is completely dangerous) 
  • PCL-5 item 19a: Blaming yourself for the stressful experience or what happened after it? 
  • PCL-5 item 19b: Blaming someone else for the stressful experience or what happened after it? 
  • PCL-5 item 14: Taking too many risks or doing things that could cause you harm? 
  • Additionally, PCL-5 item 11, Having strong negative feelings such as fear, horror, anger, guilt or shame, will be calculated based on the responses of HTQ item 10 and HSCL items 2, 9, and 12. 

7.4 Application/acceptance from the Danish Data Protection Agency, the National Committee on Health Research Ethics 

Approvals will be obtained under the randomized controlled trial at the CTP ("The effect of integrating cross-sectoral collaboration in psychosocial treatment of trauma-affected refugees; a randomised controlled trial"). 

7.5 Analysis 

Initial analyses will be based on the assumptions of the Rasch model. Both scales will be tested as unidimensional as well as two dimensional constructs based on the findings in Vindbjerg et al. (n.d.). In cases of local dependence and DIF, the model will be extended to accommodate this in the form of a graphical log-linear Rasch model (Kreiner & Christensen, 2002). In cases of item misfit, we evaluate if the added DSM-5 items display evidence of over- or underdiscrimination. Finally, the reliability of the fitted scales are compared to evaluate the potentially added reliability offered by the additional DSM-5 items. 

8. Expected results 

Based on previous results, we expect responses to both the original and extended DSM-5 scale to approximate fit to a two-dimensional model. We expect the added items of the DSM-5 to the numbing cluster to improve the reliability of the scale, while also allowing for a more detailed analysis of the subscale structure. 

9. Dissemination of results 

Results will be submitted for publication in an international peer-reviewed journal. 

10. References 

  • Blevins, C. A., Weathers, F. W., Davis, M. T., Witte, T. K., & Domino, J. L. (2015). The Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5): Development and Initial Psychometric Evaluation. Journal of Traumatic Stress, 28, 489–498. 
  • Kreiner, S., & Christensen, K. B. (2002). Graphical Rasch Models. In M. Mesbah, B. F. Cole, & M.-L. T. Lee (Eds.), Statistical Methods for Quality of Life Studies (pp. 187–203). https://doi.org/10.1007/978-1-4757-3625-0 
  • Vindbjerg, E., Carlsson, J., Mortensen, E. L., Elklit, A., & Makransky, G. (2016). The latent structure of post-traumatic stress disorder among Arabic-speaking refugees receiving psychiatric treatment in Denmark. BMC Psychiatry, 16(309), 1–10. https://doi.org/10.1186/s12888-016- 0936-0 
  • Vindbjerg, E., Mortensen, E. L., Carlsson, J., Makransky, G., Mortensen, E. L., & Makransky, G. (n.d.). A Rasch-based validity study of the Harvard Trauma Questionnaire. Manuscript Submitted for Publication.
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