A factor analytic evaluation of the World Health Organization Disability Assessment Schedule 2.0 among veterans presenting to a generalist mental health clinic
Introduction
Functional impairments are fundamental elements of mental health diagnostic criteria. However, with the change to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5; American Psychiatric Association, 2013), the multiaxial system has been eliminated. Moving to a nonaxial diagnostic system signified the demise of the Global Assessment of Functioning (GAF) scale. In the absence of the GAF scale, DSM-5 proposes use of the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0; Ustun et al., 2010) to measure functional impairment and to guide clinical decision making in a more reliable manner. The WHODAS 2.0 is frequently employed within the VA and the Veterans Benefits Administration (VBA) to assist in informing treatment recommendations and disability assessments for determination of service connection associated with conditions caused or exacerbated by military service. However, the factor structure of the scale has yet to be evaluated among clinical Veteran populations and warrants further evaluation to ensure the instrument is psychometrically robust with this population. Establishing the validity of the WHODAS 2.0 with VA utilizers is particularly salient given that in 2015, an estimated nine million Veterans were enrolled in VA care (Department of Veterans Affairs, 2017).
The widely used WHODAS 2.0 has the potential to be a gold-standard assessment of functional impairments and facilitate greater standardization and replicability of the construct of disability. Central to the development of the WHODAS 2.0 was the International Classification of Functioning, Disability, and Health (ICF) and reliance on item-response theory for item selection and interpretation. Through the utilization of the ‘complex’ version of scoring, the measure may be proxy, clinician- or self-administered to obtain a total score and comparative estimates of functioning within six domains: cognition, mobility, self-care, getting along, life activities, and participation in society. While reliability and several aspects of validity have been widely reported throughout 19 countries (Ustun et al., 2010), very few examinations replicating the original factor structure have been conducted.
In addition to the paucity of factor analytic studies that have been published, extant research has been mixed. For examples, Federici et al. (2009) did not confirm the originally proposed factor structure of the WHODAS 2.0 in ’normal’ and rehabilitation patients, respectively. Similarly, a study of rural Ethiopian participants experiencing severe mental disorders (Habtamu et al., 2017) found the factor structure of the 36-item scale did not reach recommended levels to substantiate satisfactory goodness of fit. In contrast, Garin et al. (2010) research with chronic disease patients derived from seven European centers demonstrated a satisfactory model fit. Using a sample stratified for the presence or absence of mental health symptoms, Buist-Bouwman et al. (2008), demonstrated a reduced model of six factors and removal of four items provided the best fit though the version utilized in this research was a modified version of the WHODAS 2.0, the 30-item European Study of the Epidemiology of Mental Disorders World Health Organization Disability Assessment Scale (ESEMeD WHODAS).
To-date, only one study has examined the factor structure of the 36-item clinician-administered version of the WHODAS 2.0 with Veterans. Marx et al. (2015) utilized confirmatory factor analyses to contrast the performance of the WHODAS 2.0 and the Inventory of Psychosocial Functioning (IPF) among 177 U.S. Veterans pursuing compensation for Posttraumatic Stress Disorder (PTSD). They found an adequate fit for both measures with the WHODAS 2.0 scores explaining 55% of the variance, however, the authors caution that the incorporation of medical and mental disorder items may be of more limited utility in determining functioning secondary to military-related mental health problems in a population with notable medical morbidities. These inconsistent results, coupled with the absence of research of general mental health treatment-seeking VA clinical mental health patients rather than PTSD-specific compensation-seeking participants utilizing VBA services indicate further research is warranted prior to concluding that the original factor structure of the WHODAS 2.0 has been demonstrated for use with clinical Veteran populations.
To examine the robustness of the validity of WHODAS 2.0 among a clinical sample of Veterans seeking general mental health services, we aimed to evaluate the factor structure of this measure and to contrast the psychometric properties between the originally proposed factors identified by the scale developers with our empirically derived model.
Section snippets
Participants and procedure
Participants were 464 Veterans referred for generalist Mental Health Clinic (MHC) services at a U.S. Veterans Healthcare Administration (VHA) hospital between January 2014 and June 2015. According to U.S. Code, Title 38, Veterans’ Benefits (1958), a veteran is defined as “a person who served in the active military, naval, or air service, and who was discharged or released therefrom under conditions other than dishonorable.” The Veterans Health Care Administration has been tasked with providing
Demographic and mental health characteristics
Veterans were primarily male, unmarried, and Caucasian. The average age was 48 years and 17.6% were 65 or older Those 65 and above endorsed significantly higher disability in the domains of self-care, non-work life activities, and total scores. A majority of the population was working or attending school (57%), although a substantial minority indicated non-work/non-student status. Persian Gulf War (including Operation Iraqi Freedom / Operation Enduring Freedom Veterans) were most frequently
Discussion
The present study supports the psychometric robustness of the factor structure of the WHODAS 2.0 among a Veteran population presenting for general mental health services in a large sample. Our findings generally support prior factor analytic research with the WHODAS 2.0 (Ustun et al., 2010), and demonstrate that a suitable factor structure can be identified and replicated using exploratory and confirmatory analyses with Veterans. We provided additional evidence for its structure among Veterans,
Funding
The Mental Health Service at VA Ann Arbor Healthcare System and the University of Michigan Department of Psychiatry supported this research. The contents do not represent the views of the U.S. Department of Veterans Affairs or the United States Government. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Conflicts of interest
There are no conflicts of interest to disclose.
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