Psychometric properties of the World Health Organization Disability Assessment Schedule in people with multiple sclerosis

Abstract

BACKGROUND:

The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) 12-item version is a generic self-report instrument measuring perceived individual functioning and disability. Studies suggest that the WHODAS 2.0 12-item version may exhibit a varying factor structure and psychometric properties depending upon the disability group studied.

OBJECTIVE:

The objective of this study was to examine the measurement structure and psychometric properties of the WHODAS 2.0 12-item version in a community sample of individuals with multiple sclerosis (MS).

METHODS:

Participants included 256 individuals with MS. Exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and concurrent validity analysis were used to psychometrically validate the measure.

RESULTS:

Results of the EFA suggest that the WHODAS 2.0 12-item version exhibits a two-factor structure in persons with MS (self-care functioning and social and cognitive functioning). These results were confirmed with the CFA (with modifications). Concurrent validity analysis revealed that the factors were significantly associated with relevant psychosocial variables in the expected directions.

CONCLUSIONS:

The WHODAS 2.0 12-item version may provide valuable information for vocational rehabilitation counselors to better support people with MS as they work toward their psychosocial and employment goals.

Keywords

Multiple sclerosis disability assessment functioning ICF

1 Introduction

Multiple sclerosis (MS) is the most common chronic, progressive, immune-mediated neurological disease in the world, and it is characterized by a variety of physical, cognitive, and emotional symptoms (Courtney et al., 2009; Day et al., 2016; Goverover et al., 2017; Olek, 2016; Rosati, 2001; Stern et al., 2010). It is estimated that more than 2.5 million individuals worldwide and approximately 400,000 individuals within the United States live with MS (Dennison et al., 2009; National Multiple Sclerosis Society[NMSS], 2017). Due to its widespread and chronic nature, an understanding of MS’s psychosocial impact is paramount to ensuring that individuals living with the disease achieve their independent living, employment, and quality of life goals.

Although no symptoms appear to be entirely unique to MS, several motor, cognitive, and neuropsychiatric disruptions have been found to be highly characteristic of the disease. Due to differences in demyelination of nerve fibers across individuals, the symptoms and course of MS tend to be idiosyncratic and unpredictable (Dennison et al., 2009; NMSS, 2017; Olek, 2016). Primary symptoms (i.e., those directly resulting from demyelination in the central nervous system [CNS]) include: spasticity, difficulties with speech and swallowing, bowel and bladder problems, pain, visual problems, cognitive difficulties, and fatigue (Conrad et al., 2012; Goverover et al., 2017). Secondary symptoms tend to include loss of balance, decreases in activities of daily living (ADL) and instrumental activities of daily living (IADL), and depression and anxiety. Symptoms due to the chronicity of a disease, or tertiary symptoms, may include social isolation, unemployment, and shifts in roles and responsibilities (Goverover et al., 2017).

Multiple sclerosis is categorized into four subtypes based on pattern and course of disease: clinically isolated syndrome (CIS), relapsing-remitting MS (RRMS), secondary-progressive MS (SPMS), and primary-progressive MS (PPMS; Courtney et al., 2009; Goverover et al., 2017). Clinically isolated syndrome is the initial episode of disease which exhibits neurologic features of inflammatory demyelination in the CNS (NMSS, 2017; Olek, 2016). Though symptoms are characteristic of MS, at this initial onset they are yet to completely fulfill diagnostic criteria (Lublin et al., 2014). Relapsing-remitting MS is characterized by defined periods of relapse or acute neurological dysfunction followed by stabilization or recovery from symptoms that is either complete or partial with sequela (Goverover et al., 2017; Olek, 2016). About 85 to 90% of individuals with MS have a relapsing-remitting course at onset (Courtney et al., 2009; Olek, 2016; Weinshenker, 1994). Secondary-progressive MS is characterized by a steady, insidious worsening of neurological functioning with few or no relapses (Courtney et al., 2009; Goverover et al., 2017; Olek, 2016). Through a span of 10 to 20 years after onset, most individuals with RRMS transition to SPMS, though there are no established criteria to determine when this shift occurs (Lublin et al., 2014; Olek, 2016). Primary progressive MS represents about 10% of individuals with MS and is characterized by a steady and progressive neurologic deterioration and accumulation of disability (Goverover et al., 2017; Koch et al., 2010; Olek, 2016).

Due to the unpredictable nature of disease course in conjunction with severity of symptoms, frequency of relapse, and usual onset in young adulthood (typically between the ages of 20 and 50; NMSS, 2017), individuals with MS may experience psychosocial difficulties, emotional disturbances, and increased levels of disability leading to significant challenges in daily life (Dennison et al., 2009). Utilizing the World Health Organization (WHO) International Classification of Functioning, Disability, and Health (ICF) allows researchers and clinicians to consider how MS may affect all the domains of functioning in an individual’s life, and how those domains interact with each other to affect community participation, including employment. The ICF model is a biopsychosocial framework for conceptualizing and classifying functioning and disability with an emphasis on the interaction between health conditions and person-environment contextual factors (Alford et al., 2015; WHO, 2001). The ICF model provides a coherent view of health by addressing biological, social, and individual perspectives (Chan & Ditchman, 2013; Chan et al., 2009; Peterson, 2005; WHO, 2001). Through this biopsychosocial approach, the ICF serves not as a classification of people, but rather as a classification of health characteristics which incorporates individual characteristics and environmental influences at the individual, institutional, and social levels. As defined by the ICF, disability, the overarching term for impairments, activity limitations, and participation restrictions, is the negative interaction between a health condition and person-environment contextual factors (WHO, 2001). As such, disability has direct and important practical implications for individuals as well as health and rehabilitation professionals as they work together to define care and treatment interventions for persons with MS (Thompson & Hobart, 1998).

Disability in MS can be measured using a variety of scales. These are classified as disease-specific disability scales such as Kurtzke’s Expanded Disability Status Scale (EDSS; Kurtzke, 1983) and the Multiple Sclerosis Functional Composite (MSFC; Cutter et al., 1999; Fischer et al., 1999), or generic measures such as the Barthel Index (BI; Mahoney & Barthel, 1965) and the Community Dependency Index (CDI; Eakin & Baird, 1995; Nicholl et al., 2004). As these measures focus more specifically on functional disability, they do not address interactions between social, personal, and environmental factors which may also influence an individual’s functioning.

Addressing these concerns and grounded in the conceptual framework of the ICF, the World Health Organization Disability Assessment Schedule (WHODAS) 2.0 is a generic self-report instrument measuring perceived individual functioning and disability across six life domains: Cognition, Mobility, Self-Care, Getting Along, Life Activities, and Participation (Üstün et al., 2010). The WHODAS 2.0 asks participants to indicate how much difficulty they have experienced in the last 30 days across the six domains. An additional three questions ask participants to indicate the total number of days, out of the last 30, they have experienced said difficulties. The WHODAS 2.0 is available in two formats: a 36-item instrument and a 12-item brief version which is recommended in situations where time constraints are present (Üstün et al., 2010). The present study will focus on the validation of the 12-item version. As reported in the WHODAS 2.0 manual, the 12-item version explains 81% of the variance of the 36-item version (Üstün et al., 2010). Further, it is reported that the WHODAS 2.0 has a two-level hierarchical structure with one general disability factor diverging into the six domains (or subscales); though it should be noted this refers to the 36-item version as the structure of the 12-item version is not discussed at length by the authors. Extensive field tests reported in the manual indicate strong evidence for test-retest reliability and internal consistency as well as face, concurrent, and construct validity for the full-version instrument.

Several researchers have investigated the psychometric properties and factor structure of the 12-item version of the WHODAS 2.0 among individuals with specific chronic health conditions and disabilities. The one-factor structure has been supported in German patients with myocardial infarction (Kirchberger et al., 2014), in Italian neurosurgical patients (Schiavolin et al., 2014), and in Spanish patients with a major depressive episode (Luciano et al., 2010). Contrary to these findings, however, in a community population of individuals with spinal cord injuries, Smedema, Ruiz, and Mohr (2017) found that the factor structure of the WHODAS 2.0 12-item version is not a unidimensional “general disability” measure, but rather comprises a three-factor structure consisting of Activities/Participation, Self-Care, and Mobility. Similarly, Smedema et al. (2016) examined the 12-item version in a community population of individuals with fibromyalgia syndrome and also found it to not exhibit a one-factor structure, but rather a two-factor structure comprising (a) Social and Cognitive Functioning and (b) Self-Care Functioning.

Recognizing the increased use of the WHODAS 2.0 in persons with MS and lack of validation of the instrument in this population, Magistrale et al. (2015) examined the psychometric properties of the 36-item version in persons with MS using both traditional (Cronbach’s alpha) and modern (item response theory [IRT]) analyses. Researchers found Cronbach’s alpha coefficients to vary between.68 (getting along with others) and.96 (life activities in work/school), suggesting low to excellent internal consistency reliability of the subscales. Rasch model IRT analyses resolved three out of the six primary domains. Due to high floor effects, understanding and community, self-care, and getting along were unresolved. Magistrale et al. (2015) concluded that despite questionable reliability of some subscales and limitations in item redundancy, the WHODAS 2.0 was a reliable and valid instrument in the assessment of self-reported disability in persons with MS.

Though researchers have examined the psychometric properties of the 36-item version in a population of individuals with MS, the 12-item self-reported version has not been evaluated for factor structure or for use in persons with MS. The purpose of this study, therefore, was to examine the measurement structure and psychometric properties of the WHODAS 2.0 12-item version in a community sample of individuals with MS.

2 Methods

2.1 Participants

Participants in this study included 256 individuals with MS who were recruited from two regional chapters of the National Multiple Sclerosis Society (NMSS) including the Greater Washington D.C./Maryland Chapter in Washington D.C. and the Wisconsin Chapter in Hartland, Wisconsin. The mean age of the participants was 44.84 years (SD = 11.17). Most of the participants were women (85.5%), married (52%), and white (85.2%). Participants in the current study were relatively well-educated with 84.4% having some college education, two- or four-year college degrees, or graduate degrees. Forty-nine percent of the participants were employed either part-time or full-time. The majority of participants (83.1%) experienced RRMS. A detailed description of participant characteristics is presented in Table 1.

Table 1
Participants’ demographic and MS characteristic (N = 243)

Variable N (%) M (SD)

Age 44.71 9.83

Gender

Male 35 (14.4%)

Female 208 (85.6%)

Race

Africa American 21 (8.6%)

Asian American/Pacific Islander 43 (1.6%)

Caucasian 207 (85.19%)

Latino/Hispanic 7 (2.9%)

Native American 2 (0.8%)

Others 3 (1.2%)

Marital status

Single 54 (22.22%)

Married 26 (51.85%)

Divorced 28 (11.52%)

Cohabiting 21 (8.2%)

Others 14 (5.7%)

Type of MS

A relapsing-remitting MS 205 (84.36%)

Secondary-progressive MS 31 (12.76%)

Primary-progressive MS 7 (2.9%)

Employment status

Full-time employed 91 (37.4%)

Part-time employed 28 (11.5%)

Unemployed 52 (21.40%)

Retired 41 (16.87%)

Full-time homemaker 14 (5.76%)

Seeking employment 9 (3.70%)

Student 5(2.05%)

Education level

Less than High School 3 (1.23%)

High school/GED 36 (14.81%)

Some college 60 (24.69%)

2-year College Degree 25 (10.29%)

4-year College Degree 71 (29.22%)

Master Degree 38 (15.64%)

Professional Degree 10 (4.11%)

(JD, MD, Ph. D)

Variable	N (%)	M	(SD)
Age		44.71	9.83
Gender
Male	35 (14.4%)
Female	208 (85.6%)
Race
Africa American	21 (8.6%)
Asian American/Pacific Islander	43 (1.6%)
Caucasian	207 (85.19%)
Latino/Hispanic	7 (2.9%)
Native American	2 (0.8%)
Others	3 (1.2%)
Marital status
Single	54 (22.22%)
Married	26 (51.85%)
Divorced	28 (11.52%)
Cohabiting	21 (8.2%)
Others	14 (5.7%)
Type of MS
A relapsing-remitting MS	205 (84.36%)
Secondary-progressive MS	31 (12.76%)
Primary-progressive MS	7 (2.9%)
Employment status
Full-time employed	91 (37.4%)
Part-time employed	28 (11.5%)
Unemployed	52 (21.40%)
Retired	41 (16.87%)
Full-time homemaker	14 (5.76%)
Seeking employment	9 (3.70%)
Student	5(2.05%)
Education level
Less than High School	3 (1.23%)
High school/GED	36 (14.81%)
Some college	60 (24.69%)
2-year College Degree	25 (10.29%)
4-year College Degree	71 (29.22%)
Master Degree	38 (15.64%)
Professional Degree	10 (4.11%)
(JD, MD, Ph. D)

2.2 Measures

2.2.1 Functional disability

Activity limitations of individuals with chronic health conditions and disabilities were measured using the 12-item version of The World Health Organization Disability Assessment Schedule (WHODAS 2.0;Üstün et al., 2010). The WHODAS 2.0 12-item version is a 12 item measure (e.g., “How much difficulty have you had in the past 30 days in performing the following activities?”), with each item rated on a 5-point Likert scale (1 = none to 5 = extreme or cannot do). Items assess functioning in six major life domains: (a) cognition (e.g., “Learning a new task, for example, learning how to get to a new place”); (b) mobility (e.g., “Walking for long distance such as a mile or equivalent?”); (c) self-care (e.g., “Washing your whole body?”); (d) getting along (e.g., “Maintaining a friendship?”); (e) life activities/household and life activities/work (e.g., “Taking care of household responsibilities?”); and (f) participation (e.g., “Your day-to-day work activities?”). The internal consistency for a mental health disability subgroup is excellent with a Cronbach’s alpha coefficient of.98 for the overall scale and good internal consistency estimates at the domain levels: cognition (0.94), mobility (0.93), self-care (0.92), getting along (0.94), life activities/household (0.92), life activities/work (0.94), and participation (0.93; Üstün et al., 2010). The overall internal consistency reliability coefficient (Cronbach’s alpha) for the WHODAS 2.0 12-item version in the present study was computed to be 0.90.

2.2.2 Fatigue

Fatigue was measured using the abbreviated version of the Modified Fatigue Impact Scale (MFIS; Larson, 2013). The brief MFIS is a five-item measure (e.g., “Because of my fatigue during the past four weeks I have been less alert”), with each item rated on a 5-point Likert scale (0 = never to 4 = always). Fatigue scores are computed by averaging the MFIS items, with higher scores indicating greater levels of fatigue. The Cronbach’s alpha coefficient for MFIS in the present study was computed to be 0.90.

2.2.3 Pain intensity

Pain intensity was measured using a four-item version of the Numeric Pain Scale (NPS; Castarlenas et al., 2017; Childs et al., 2005). The NPS captures present levels of pain intensity (e.g., “How would you rate your pain right now?”) and past week pain (e.g., “How would you rate your worst level of pain during the last week?”), with each item rated on an 11-point Likert scale (0 = no pain to 10 = worst imaginable pain). Pain scores are computed by averaging the four items, with higher scores indicating greater levels of pain. The Cronbach’s alpha coefficient for the NPS in the present study was computed to be 0.94.

2.2.4 Sleep problems

Sleep difficulty was measured using an abbreviated version of the Medical Outcomes Study-Sleep Scale (MOS-Sleep; Hays & Stewart, 1992). The MOS-Sleep Scale is comprised of four items (e.g., “How often during the past 4 weeks did you feel that your sleep was not quiet [moving restlessly, feeling tense, speaking, etc., while sleeping?”]), with each item rated on a 6-point Likert scale (1 = none of the time to 6 = all of the time). Sleep difficulty scores are computed by averaging all four items, with higher scores indicating greater levels of sleep difficulty. The Cronbach’s alpha coefficient for MOS-Sleep in the present study was computed to be 0.63.

2.2.5 Depression

Depression was measured using the Patient Health Questionnaire-4 (PHQ-4; Kroenke et al., 2009). The PHQ-4 is comprised of four items (e.g., “Over the last 2 weeks, how often have you been bothered by feeling nervous, anxious or on edge?”), with each item rated on a 4-point Likert scale (0 = not at all to 3 = nearly everyday). Depression scores are calculated by summing the items, with higher scores indicating greater levels of depression. The Cronbach’s alpha coefficient for PHQ-4 in the present study was computed to be 0.89.

2.2.6 Stress

Stress was measured using an abbreviated version of the Perceived Stress Questionnaire (PSQ; Levenstein et al., 1993). The PSQ is comprised of nine items (e.g., “During the past month, have you felt under pressure from deadlines?”), with each item rated on a 4-point Likert scale (1 = almost never to 5 = usually). Stress scores are calculated by averaging the nine items, with higher scores indicating greater levels of stress. The Cronbach’s alpha coefficient for the PSQ in the present study was computed to be 0.84.

2.2.7 Social support

Perceived social support was measured using the Interpersonal Support Evaluation List (ISEL-12; Cohen et al., 1985). The ISEL is comprised of 12 items (e.g., “If I wanted to go on a trip for a day [for example, to the country or mountains], I would have a hard time finding someone to go with me.”), with each item rated on a 4-point Likert scale (0 = definitely false to 3 = definitely true). Social support scores are calculated by averaging the items, with higher scores indicating greater levels of perceived social support. The Cronbach’s alpha coefficient for ISEL-12 in the present study was computed to be 0.86.

2.2.8 Community participation

Community participation was measured using the Brief Multiple Sclerosis Community Participation Scale (MSCPS; Wu et al., 2019). It is comprised of 13 meaningful life role items: (a) employment (full-time), (b) employment (part-time), (c) volunteer work, (d) spouse, (e) parent, (f) children, (g) student, (h) recreation activities, (i) getting around, (j) live independently, (k) social life, (l) church member, and (m) engage in health promoting activities, with each item rated on a 6-point Likert scale (0 = not important, 1 = much lower than I would like to do, 2 = slightly lower than I would like to do, 3 = consistent with what I would like to do, 4 = better than I would like to do, 5 = much better than I would like to do). The MSCPS assesses the importance and the extent of participation by the person in each relevant meaningful life role. Each life role is also weighted by its relative importance score and summed to yield a total participation score ranging from 1-5. The Cronbach’s alpha coefficient for MSCPS in the present study was computed to be 0.78.

2.3 Statistical analysis

Listwise deletion was used to remove all data for any case with one or more missing values. Data were split into to two halves, the validation sample (N = 100) was used to perform an exploratory factor analysis (EFA) for the WHODAS 2.0 and confirmatory factor analysis (CFA) was conducted to confirm the EFA finding in a cross-validation sample (N = 143) using the Latent Variable Analysis (lavaan) package in R (Rosseel, 2012). Pearson product-moment correlation was used to evaluate the relationship between functional disability and other related constructs (e.g., community participation) in the nomological network (Cronbach & Meehl, 1955).

3 Results

3.1 Exploratory factor analysis

The WHODAS 2.0 12-item version was subjected to a principal components analysis (PCA) with oblique rotation. The Kaiser– Meyer– Olkin (KMO) measure of sampling adequacy was.79 (>.60), exceeding the minimum criterion of.50, and the Bartlett’s test of sphericity was significant, χ² (66, N = 243) = 619.45, p < 0.001, indicating that correlations in the data set are appropriate for factor analysis. Both the Kaiser– Guttman “eigenvalues greater than one” criterion and Cattell’s scree test (Cattell, 1966; Nunnally & Bernstein, 1994) indicated a two-factor solution, accounting for 60.50% of the total variance. In addition, the Bayesian Information Criterion dropped dramatically from one factor (209.37) to two factor (47.08), suggesting two factor is a better solution. All items loaded significantly onto their respective factors (loadings ranging from 0.45 to 0.92). In examining the contents of the items in each factor, these two factors were labelled Social and Cognitive Functioning and Self-Care Functioning. Table 2 presents the means and standard deviations for each of the items on the WHODAS 2.0 12-item version as well as factor loadings, communality (h²), eigenvalues, percentage of variance explained, and reliability coefficients.

Table 2
Explanatory factor analysis using principal components analysis with oblique rotation

Item Self-care functioning Social and cognitive functioning Mean (SD)

8. Washing your whole body? 0.92 1.73 (1.06)

9. Getting dressed? 0.91 1.69 (0.97)

7. Walking a long distance such as a kilometer (or equivalent)? 0.70 3.25 (1.59)

1. Standing for long periods such as 30 minutes? 0.70 3.01 (1.37)

2. Taking care of your household responsibilities? 0.56 2.68 (1.08)

11. Maintaining a friendship? 0.71 1.61 (0.81)

6. Concentrating on doing something for ten minutes? 0.77 2.14 (1.00)

5. How much have you been emotionally affected by your health problems? 0.69 2.86 (1.01)

3. Learning a new task, for example, learning how to get to a new place? 0.68 2.06 (1.08)

10. Dealing with people you do not know? 0.67 1.78 (0.94)

4. How much of a problem did you have joining in community activities (for example, festivities, religious or other activities) in the same way as anyone else can? 0.46 2.26 (1.16)

12. Your day to day work? 0.45 2.27 (1.21)

Eigenvalues 6.56 1.95

% Variance 46.65 13.84

Reliability (Cronbach’s Alpha) 0.89 0.80

Mean (SD) 2.50 (0.98) 2.10(0.67)

Item	Self-care functioning	Social and cognitive functioning	Mean (SD)
8. Washing your whole body?	0.92		1.73 (1.06)
9. Getting dressed?	0.91		1.69 (0.97)
7. Walking a long distance such as a kilometer (or equivalent)?	0.70		3.25 (1.59)
1. Standing for long periods such as 30 minutes?	0.70		3.01 (1.37)
2. Taking care of your household responsibilities?	0.56		2.68 (1.08)
11. Maintaining a friendship?		0.71	1.61 (0.81)
6. Concentrating on doing something for ten minutes?		0.77	2.14 (1.00)
5. How much have you been emotionally affected by your health problems?		0.69	2.86 (1.01)
3. Learning a new task, for example, learning how to get to a new place?		0.68	2.06 (1.08)
10. Dealing with people you do not know?		0.67	1.78 (0.94)
4. How much of a problem did you have joining in community activities (for example, festivities, religious or other activities) in the same way as anyone else can?		0.46	2.26 (1.16)
12. Your day to day work?		0.45	2.27 (1.21)
Eigenvalues	6.56	1.95
% Variance	46.65	13.84
Reliability (Cronbach’s Alpha)	0.89	0.80
Mean (SD)	2.50 (0.98)	2.10(0.67)

Factor 1 – Self-Care Functioning. This factor accounted for 46.65% of the total variance. It is comprised of five items, reflecting self-care functioning (e.g., “Taking care of household responsibilities?”). The mean rating for this factor was 2.50 (SD = 0.98). The Cronbach’s alpha for this factor was computed to be 0.89.

Factor 2 – Social and Cognitive Functioning. This factor accounted for 13.59% of the total variance. This factor comprised of seven items, reflecting social functioning (e.g., “How much of a problem did you have joining in community activities [for example, festivities, religious or other activities] in the same way as anyone else can?”) and cognitive functioning (e.g., “Concentrating on doing something for ten minutes?”). The mean rating for this factor was 2.10 (SD = 0.67). The Cronbach’s alpha for this factor was computed to be 0.80.

3.2 Confirmatory Factor Analysis

To study the stability of the EFA, we conducted CFA on the second data set (N = 143), analyzing the items for WHODAS 2.0. The two-factor model initially indicated a less than good fit model: χ² (53, N = 143) = 241.41, p < 0.000; χ²/df = 4.55, comparative fit index (CFI) = 0.813; and the root mean square error of approximation (RMSEA) = 0.158, 90% confidence interval (CI; 0.138, 0.178). An examination of modification indexes suggested that three pairs of error terms should be correlated: Item e8 (“Washing your whole body”) with Item e9 (“Getting dressed”), followed by Item e10 (“Dealing with people you do not know?”) with Item e11 (“Maintaining a friendship?”). In addition, Item e2 (“Taking care of your household responsibilities?”) and Item e12 (“Your day to day work”) could be considered as cross-loaders. Correlated errors frequently occur with items using similar wording or appearing in close physical proximity to each other on the questionnaire (Bollen & Lennox, 1991). The chi-square yielded an optimal model fit after these modifications, with χ² (49, N = 143) = 88.197, p < 0.001, χ²/df = 1.80 is less than 3, CFI of.961 (>0.95), and RMSEA of 0.075 (<0.08) (90% CI [0.075, 0.120]). All these indexes meet the criteria of good model fit (cf., Weston et al., 2008).

3.3 Concurrent validity analysis

The self-care functioning factor was positively associated with the social and cognitive functioning factor found in this study (r = 0.62, p < 0.01), fatigue (r = 0.52, p < 0.01), pain intensity (r = 0.43, p < 0.01), sleep problems (r = 0.30, p < 0.01), and depression (r = 0.28, p < 0.01), and negatively associated with community participation (r = –0.66, p < 0.01) and social support (r = –0.24, p < 0.01). The social and cognitive functioning factor was positively associated with the self-care functioning factor (r = 0.62, p < 0.01), fatigue (r = 0.75, p < 0.01), pain intensity (r = 0.52, p < 0.01), sleep problems (r = 0.50, p < 0.01), stress (r = 0.46, p < 0.01), and depression (r = 0.58, p < 0.01) and negatively associated with community participation (r = –0.68, p < 0.01) and social support (r = –0.34, p < 0.01). Functional disability was associated with related constructs in the expected directions. These results support the construct validity of the WHODAS 2.0 12-item version.

4 Discussion

Results of this study revealed a two-factor structure of the WHODAS 2.0 12-item version in a sample of people with MS. The two factors consist of social and cognitive functioning and self-care functioning. This two-factor structure is consistent with previous research on people with fibromyalgia syndrome (Smedema et al., 2016). In contrast, the WHODAS 2.0 12-item version has displayed different factor structures across other disability populations (Smedema et al., 2016). For example, several studies (cardiac rehabilitation patients, neurosurgical patients, and persons with major depressive disorders) found a one-factor solution (e.g., Kirchberger et al., 2014; Üstün et al., 2010), whereas a study with a community sample of individuals with spinal cord injury displayed a three-factor structure (Smedema et al., 2017). These research studies suggest that the WHODAS 2.0 12-item version may display different structural characteristics depending on different types of chronic health conditions and disabilities (Smedema et al., 2016, 2017). These discrepancies in factor structures are undoubtedly due to differential functional limitations, symptom profiles, and health and functional consequences that vary based upon disability type.

The concurrent validity analysis demonstrated that the two factors were associated with several biopsychosocial variables. As expected, both factors were found to be positively associated with fatigue, pain intensity, sleep problems, and depression, and negatively associated with community participation and social support. Additionally, the self-care functioning factor was positively associated with the social and cognitive functioning factor. Both factors are most strongly related to fatigue and community participation, suggesting that the impact of disability in persons with MS may be more affected by feeling tired and engaging in meaningful life role activities. Indeed, fatigue is widely known as the most common and one of the most intrusive symptoms of MS (Rumrill & Bishop, 2019), and the deleterious impact that MS has on community participation and engagement is similarly well-documented (Kalb, 2016).

Findings from this study suggest that the WHODAS 2.0 12-item version is a valid measure of disability and functional impairment to administer to individuals with MS. Further, findings provide support that researchers and clinicians can utilize this instrument to address some of the most important health and functional consequences of MS. Specifically, researchers and clinicians can use the total score for assessing the overall impact of disability in individuals with MS, then they can work in partnership with clients to identify specific psychosocial and vocational interventions that address clients’ multiple and varied MS symptoms. In addition, if researchers and clinicians would like to focus on examining social and cognitive functioning or self-care functioning (two other critically important issues facing people with MS (Kalb, 2016), they can use the individual subscales accordingly. Future research is warranted to further examine this scale’s measurement properties and clinical utility in individuals with MS.

Although the results demonstrated the WHODAS 2.0 12-item version as a promising assessment for people with MS, there are several conceptual considerations to keep in mind. The instrument was developed based on an enablement framework; however, the items were written in a more disablement approach (Chan et al., 2009; Smedema et al., 2016). Smedema and colleagues (2017) suggested that the items could be rephrased with a more enablement orientation to align better with the positively framed ICF model, such as asking what respondents are able to do rather than what they have difficulty doing. Another consideration is that the distinction between “activities” (e.g., taking care of household responsibilities) and “participation” (e.g., day-to-day work activities) should be more clearly defined and assessed in the WHODAS 2.0 12-item version (Smedema et al., 2016). Gaskin, Lambert, Bowe, and Orellana (2017) also indicated that the WHODAS 2.0 measures the severity of disability but not the degree of functioning. Therefore, the operationalization of functioning and disability within the ICF model should be further examined.

4.1 Limitations

Although the findings of this study are promising, there are several limitations that bear mentioning. First, results were gathered from an online survey with a convenience sample, which calls into question external validity or generalization. Most of the participants were White, well-educated females who were members of the advocacy organization NMSS. These individuals may not entirely reflect the characteristics and perspectives of the broader population of people with MS. Second, participants who responded to the survey were more likely to experience higher levels of functioning than the general MS population. Those who had more severe symptoms and functional limitations related to fatigue and/or cognition may have had difficulty attempting, navigating, and completing the survey. A third limitation is that this was a self-report survey, which can introduce social desirability, subjectivity, and recall biases. Participants may have been reluctant to respond in ways that might have been viewed as unfavorable by the research team. Additionally, it may be possible that certain cognitive/functional limitations affected participants’ abilities to indicate their responses.

4.2 Implications for rehabilitation counseling practice

Multiple sclerosis is a complex, dynamic, autoimmune disease that affects an individual’s functioning across multiple domains; therefore, conceptualizing it from a biopsychosocial framework such as the ICF can allow people with MS, clinicians, and researchers to better understand its impact from multiple perspectives (Holper et al., 2010; Wijenberg et al., 2016). Due to its brief nature, the WHODAS 2.0 12-item version may be a convenient and useful tool in assessing the overall impact of a person’s MS, and may be particularly useful in identifying limitations in regard to social and cognitive functioning and self-care. Once these barriers are identified, the WHODAS 2.0 12-item version can help rehabilitation counselors with the selection and/or development of specific interventions to promote employment and other important vocational rehabilitation outcomes. Social skills training and self-management designed to promote cognitive, social, and self-care functioning are some examples of interventions that may be utilized (Bishop et al., 2009; Lorefice et al., 2018; Strober et al., 2018). Rehabilitation counselors can integrate the WHODAS 2.0 12-item version into the rehabilitation process to gain a holistic understanding of functioning in clients with MS, which can guide treatment planning and service coordination. For instance, rehabilitation counselors can better support people with MS by providing counseling, job placement assistance, job skills training, workplace support, and facilitating discussions related to work accommodation and assistive technology (Chiu et al., 2013; Inge et al., 2016).

5 Conclusion

Findings from this study add to the existing literature by providing support for using the WHODAS 2.0 12-item version to assess social and cognitive functioning and self-care functioning in individuals with MS. Additionally, numerous biopsychosocial variables were found to be correlated with the self-care functioning factor as well as the social and cognitive functioning factor. These results suggest that the integration of the WHODAS 2.0 12-item version into vocational rehabilitation counseling practices may provide valuable information for rehabilitation counselors to better support people with MS as they work toward their psychosocial and employment goals.

Conflict of interest

None to report.

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