Linking job duties, functioning, and employment status using the Work-Disability Functional Assessment Battery (WD-FAB): An expert coding and quantitative analysis.

BACKGROUND: An understanding of the link between specific occupational demands and individual worker functioning is limited, although such information could permit an assessment of the fit between the two in a manner that would inform national and state disability programs such as vocational rehabilitation and Social Security disability programs. OBJECTIVE: Our goal was to examine the utility of assessing physical and mental functioning relative to self-reported job duties to identify the domains of worker functioning most likely to create barriers to fulfilling an occupation's specific requirements. METHODS: Through primary survey data collection, 1770 participants completed the Work-Disability Functional Assessment Battery (WD-FAB) instrument after reporting details on their occupations (or most recent occupation if not working). Expert coders evaluated the level of function expected to successfully carry out each self-reported job duty with respect to six scales of physical and mental function. Quantitative analysis is used to examine the relationship between functioning and job duties. RESULTS: Those not working due to disability were more likely to fall short of the threshold of the physical and mental functioning requirements of their last job's three main job duties compared to those currently employed. Mental function scales were most likely to be the area experiencing a shortfall. CONCLUSIONS: Functional difficulties impede the ability to continue working in particular jobs that require that ability. This points to a need for specific accommodations to be implemented to bridge the gap between job requirements and functional capacity so that workers may remain engaged in their current work.

Regularized Bayesian calibration and scoring of the WD-FAB IRT model improves predictive performance over marginal maximum likelihood.

Item response theory (IRT) is the statistical paradigm underlying a dominant family of generative probabilistic models for test responses, used to quantify traits in individuals relative to target populations. The graded response model (GRM) is a particular IRT model that is used for ordered polytomous test responses. Both the development and the application of the GRM and other IRT models require statistical decisions. For formulating these models (calibration), one needs to decide on methodologies for item selection, inference, and regularization. For applying these models (test scoring), one needs to make similar decisions, often prioritizing computational tractability and/or interpretability. In many applications, such as in the Work Disability Functional Assessment Battery (WD-FAB), tractability implies approximating an individual's score distribution using estimates of mean and variance, and obtaining that score conditional on only point estimates of the calibrated model. In this manuscript, we evaluate the calibration and scoring of models under this common use-case using Bayesian cross-validation. Applied to the WD-FAB responses collected for the National Institutes of Health, we assess the predictive power of implementations of the GRM based on their ability to yield, on validation sets of respondents, ability estimates that are most predictive of patterns of item responses. Our main finding indicates that regularized Bayesian calibration of the GRM outperforms the regularization-free empirical Bayesian procedure of marginal maximum likelihood. We also motivate the use of compactly supported priors in test scoring.

At the intersection of chronic disease, disability and health services research: A scoping literature review.

BACKGROUND: There is a concerted effort underway to evaluate and reform our nation's approach to the health of people with ongoing or elevated needs for care, particularly persons with chronic conditions and/or disabilities. OBJECTIVE: This literature review characterizes the current state of knowledge on the measurement of chronic disease and disability in population-based health services research on working age adults (age 18-64). METHODS: Scoping review methods were used to scan the health services research literature published since the year 2000, including medline, psycINFO and manual searches. The guiding question was: "How are chronic conditions and disability defined and measured in studies of healthcare access, quality, utilization or cost?" RESULTS: Fifty-five studies met the stated inclusion criteria. Chronic conditions were variously defined by brief lists of conditions, broader criteria-based lists, two or more (multiple) chronic conditions, or other constructs. Disability was generally assessed through ADLs/IADLs, functional limitations, activity limitations or program eligibility. A smaller subset of studies used information from both domains to identify a study population or to stratify it by subgroup. CONCLUSIONS: There remains a divide in this literature between studies that rely upon diagnostically-oriented measures and studies that instead rely on functional, activity or other constructs of disability to identify the population of interest. This leads to wide ranging differences in population prevalence and outcome estimates. However, there is also a growing effort to develop methods that account for the overlap between chronic disease and disability and to "segment" this heterogeneous population into policy or practice relevant subgroups.

Introducing the Adults with Chronic Healthcare Needs (ACHCN) definition and screening instrument: Rationale, supporting evidence and testing.

BACKGROUND: Among working age adults in the United States, there is a large, heterogeneous population that requires ongoing and elevated levels of healthcare and related services. At present, there are conflicting approaches to the definition and measurement of this population in health services research. OBJECTIVE: An expert panel was convened by the National Institutes of Health with the objective of developing a population-level definition of Adults with Chronic Healthcare Needs (ACHCN). In addition, the panel developed a screening instrument and methods for its use in health surveys to identify and stratify the population consistently. METHODS: The panel employed multiple methods over the course of the project, including scoping literature reviews, quantitative analyses from national data sources and cognitive testing. RESULTS: The panel defined the ACHCN population as "Adults (age 18-65) with [1] ongoing physical, cognitive, or mental health conditions or difficulties functioning who [2] need health or related support services of a type or amount beyond that needed by adults of the same sex and similar age." The screener collects information on chronic health conditions, functional difficulties, and elevated use of or unmet need for healthcare services. CONCLUSIONS: Adapted from the Maternal and Child Health Bureau definition that identifies Children with Special Healthcare Needs, aligned with the ACS-6 disability measure, and consistent with the HHS Multiple Chronic Condition Framework, this definition and screener provide the research community with a common denominator for the identification of ACHCN.

Improving Assessment of Work Related Mental Health Function Using the Work Disability Functional Assessment Battery (WD-FAB).

Purpose To improve the mental health component of the Work Disability Functional Assessment Battery (WD-FAB), developed for the US Social Security Administration's (SSA) disability determination process. Specifically our goal was to expand the WD-FAB scales of mood & emotions, resilience, social interactions, and behavioral control to improve the depth and breadth of the current scales and expand the content coverage to include aspects of cognition & communication function. Methods Data were collected from a random, stratified sample of 1695 claimants applying for the SSA work disability benefits, and a general population sample of 2025 working age adults. 169 new items were developed to replenish the WD-FAB scales and analyzed using factor analysis and item response theory (IRT) analysis to construct unidimensional scales. We conducted computer adaptive test (CAT) simulations to examine the psychometric properties of the WD-FAB. Results Analyses supported the inclusion of four mental health subdomains: Cognition & Communication (68 items), Self-Regulation (34 items), Resilience & Sociability (29 items) and Mood & Emotions (34 items). All scales yielded acceptable psychometric properties. Conclusions IRT methods were effective in expanding the WD-FAB to assess mental health function. The WD-FAB has the potential to enhance work disability assessment both within the context of the SSA disability programs as well as other clinical and vocational rehabilitation settings.

Improving measures of work-related physical functioning.

PURPOSE: To expand content of the physical function domain of the Work Disability Functional Assessment Battery (WD-FAB), developed for the US Social Security Administration's (SSA) disability determination process. METHODS: Newly developed questions were administered to 3532 recent SSA applicants for work disability benefits and 2025 US adults. Factor analyses and item response theory (IRT) methods were used to calibrate and link the new items to the existing WD-FAB, and computer-adaptive test simulations were conducted. RESULTS: Factor and IRT analyses supported integration of 44 new items into three existing WD-FAB scales and the addition of a new 11-item scale (Community Mobility). The final physical function domain consisting of: Basic Mobility (56 items), Upper Body Function (34 items), Fine Motor Function (45 items), and Community Mobility (11 items) demonstrated acceptable psychometric properties. CONCLUSIONS: The WD-FAB offers an important tool for enhancement of work disability determination. The FAB could provide relevant information about work-related functioning for initial assessment of claimants; identifying denied applicants who may benefit from interventions to improve work and health outcomes; enhancing periodic review of work disability beneficiaries; and assessing outcomes for policies, programs and services targeting people with work disability.

Diagnosis isn't enough: Understanding the connections between high health care utilization, chronic conditions and disabilities among U.S. working age adults.

BACKGROUND: Under the ACA, new programs are being developed to enhance care coordination and reduce health care costs among people with chronic conditions, disabilities, and high utilization of health care. However, the relationships between these groups are not well understood. OBJECTIVES: Our aims were to (1) identify high utilizers of health care in the U.S. working age (18-64) population, (2) examine the overlap between this group and people with chronic conditions and/or disabilities, (3) identify predictors of high service use or cost among these subpopulations, and (4) recommend approaches for stratification of individuals with high health care utilization. METHODS: Using pooled national data from the Medical Expenditure Panel Survey (2006-2008), we created indices to identify elevated or high utilization and cost groups. We performed descriptive analyses, bivariate comparisons and multivariate analyses to examine the relations between these populations and individuals with chronic conditions and/or disabilities. RESULTS: While the large majority of persons with high use/cost had chronic conditions, the minority of persons with chronic conditions had high health care utilization. However, among persons with chronic conditions, disability was a significant predictor of high utilization. Annual expenditures were significantly elevated among people with disabilities, particularly when activities of daily living were limited. CONCLUSIONS: We conclude that medical diagnosis alone is insufficient for the development of eligibility criteria for, or the evaluation of, programs intended to better the delivery or coordination of services for high utilizers of health care services. New approaches are needed to assess functional limitations and identify ongoing needs for services and supports.

Work-related measures of physical and behavioral health function: Test-retest reliability.

BACKGROUND: The Work Disability Functional Assessment Battery (WD-FAB), developed for potential use by the US Social Security Administration to assess work-related function, currently consists of five multi-item scales assessing physical function and four multi-item scales assessing behavioral health function; the WD-FAB scales are administered as Computerized Adaptive Tests (CATs). OBJECTIVE: The goal of this study was to evaluate the test-retest reliability of the WD-FAB Physical Function and Behavioral Health CATs. METHODS: We administered the WD-FAB scales twice, 7-10 days apart, to a sample of 376 working age adults and 316 adults with work-disability. Intraclass correlation coefficients were calculated to measure the consistency of the scores between the two administrations. Standard error of measurement (SEM) and minimal detectable change (MDC90) were also calculated to measure the scales precision and sensitivity. RESULTS: For the Physical Function CAT scales, the ICCs ranged from 0.76 to 0.89 in the working age adult sample, and 0.77-0.86 in the sample of adults with work-disability. ICCs for the Behavioral Health CAT scales ranged from 0.66 to 0.70 in the working age adult sample, and 0.77-0.80 in the adults with work-disability. The SEM ranged from 3.25 to 4.55 for the Physical Function scales and 5.27-6.97 for the Behavioral Health function scales. For all scales in both samples, the MDC90 ranged from 7.58 to 16.27. CONCLUSION: Both the Physical Function and Behavioral Health CATs of the WD-FAB demonstrated good test-retest reliability in adults with work-disability and general adult samples, a critical requirement for assessing work related functioning in disability applicants and in other contexts.

Interpreting physical and behavioral health scores from new work disability instruments.

OBJECTIVE: To develop a system to guide interpretation of scores generated from 2 new instruments measuring work-related physical and behavioral health functioning (Work Disability - Physical Function (WD-PF) and WD - Behavioral Function (WD-BH)). DESIGN: Cross-sectional, secondary data from 3 independent samples to develop and validate the functional levels for physical and behavioral health functioning. SUBJECTS: Physical group: 999 general adult subjects, 1,017 disability applicants and 497 work-disabled subjects. Behavioral health group: 1,000 general adult subjects, 1,015 disability applicants and 476 work-disabled subjects. METHODS: Three-phase analytic approach including item mapping, a modified-Delphi technique, and known-groups validation analysis were used to develop and validate cut-points for functional levels within each of the WD-PF and WD-BH instrument's scales. RESULTS: Four and 5 functional levels were developed for each of the scales in the WD-PF and WD-BH instruments. Distribution of the comparative samples was in the expected direction: the general adult samples consistently demonstrated scores at higher functional levels compared with the claimant and work-disabled samples. CONCLUSION: Using an item-response theory-based methodology paired with a qualitative process appears to be a feasible and valid approach for translating the WD-BH and WD-PF scores into meaningful levels useful for interpreting a person's work-related physical and behavioral health functioning.

Work disability functional assessment battery: feasibility and psychometric properties.

OBJECTIVE: To assess the feasibility and psychometric properties of 8 scales covering 2 domains of the newly developed Work Disability Functional Assessment Battery (WD-FAB): physical function (PF) and behavioral health (BH) function. DESIGN: Cross-sectional study. SETTING: Community. PARTICIPANTS: Adults (N=973) unable to work because of a physical (n=497) or a mental (n=476) disability. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Each disability group responded to a survey consisting of the relevant WD-FAB scales and existing measures of established validity. The WD-FAB scales were evaluated with regard to data quality (score distribution, percentage of "I don't know" responses), efficiency of administration (number of items required to achieve reliability criterion, time required to complete the scale) by computerized adaptive testing (CAT), and measurement accuracy as tested by person fit. Construct validity was assessed by examining both convergent and discriminant correlations between the WD-FAB scales and scores on same-domain and cross-domain established measures. RESULTS: Data quality was good, and CAT efficiency was high across both WD-FAB domains. Measurement accuracy was very good for PF scales; BH scales demonstrated more variability. Construct validity correlations, both convergent and divergent, between all WD-FAB scales and established measures were in the expected direction and range of magnitude. CONCLUSIONS: The data quality, CAT efficiency, person fit, and construct validity of the WD-FAB scales were well supported and suggest that the WD-FAB could be used to assess PF and BH function related to work disability. Variation in scale performance suggests the need for future work on item replenishment and refinement, particularly with regard to the Self-Efficacy scale.

Do claimants over-report behavioral health dysfunction when filing for work disability benefits?

BACKGROND: Questions exist related to the best way to use medical evidence relative to self-report as part of the SSA disability determination process. OBJECTIVE: To examine concordance between provider and claimant responses along the four dimensions of work related behavioral health functioning: Social Interactions, Mood and Emotions, Behavioral Control, and Self-Efficacy. METHODS: Using secondary data from a larger study, which collected data on individuals reporting difficulties with work (claimants) due to mental conditions, 39 items were completed by claimants and their healthcare provider. Inter-rater agreement was assessed using three techniques: Cohen's kappa, percent absolute agreement, and folded mountain plots. RESULTS: A sample of 65 dyads was obtained. Inter-rater agreement was low for most items (k=0.0-0.20) with a minority of items having fair agreement (k=0.21-0.40) Percent agreement was fair: Mood and Emotions (46%), Self-Efficacy (44%), Behavioral Control (39%) and Social Interactions (38%). Overall, providers reported lower functioning compared to claimants for the Behavioral Control and Self-Efficacy scales; the reverse trend held for the Mood and Emotions scale. CONCLUSIONS: Results indicate discordance between provider and claimant report of behavioral health functioning. Understanding reasons for and approaches to reconciling the inconsistencies between claimant and provider perspectives is a complex task. These findings have implications for how best to assess mental and behavioral-health related work disability in the absence of an established gold standard measure.

First in line: prioritizing receipt of Social Security disability benefits based on likelihood of death during adjudication.

BACKGROUND: Given the complexity of the adjudication process and volume of applications to Social Security Administration's (SSA) disability programs, many individuals with serious medical conditions die while awaiting an application decision. Limitations of traditional survival methods called for a new empirical approach to identify conditions resulting in rapid mortality. OBJECTIVE: To identify health conditions associated with significantly higher mortality than a key reference group among applicants for SSA disability programs. RESEARCH DESIGN: We identified mortality patterns and generated a survival surface for a reference group using conditions already designated for expedited processing. We identified conditions associated with significantly higher mortality than the reference group and prioritized them by the expected likelihood of death during the adjudication process. SUBJECTS: Administrative records of 29 million Social Security disability applicants, who applied for benefits from 1996 to 2007, were analyzed. MEASURES: We computed survival spells from time of onset of disability to death, and from date of application to death. Survival data were organized by entry cohort. RESULTS: In our sample, we observed that approximately 42,000 applicants died before a decision was made on their disability claims. We identified 24 conditions with survival profiles comparable with the reference group. Applicants with these conditions were not likely to survive adjudication. CONCLUSIONS: Our approach facilitates ongoing revision of the conditions SSA designates for expedited awards and has applicability to other programs where survival profiles are a consideration.

Difference, disparity, and disability: a comparison of health, insurance coverage, and health service use on the basis of race/ethnicity among US adults with disabilities, 2006-2008.

BACKGROUND: In the United States, research on health disparities has begun to include people with disabilities as a minority population. However, there is a gap in our knowledge of whether, and to what extent, racial and ethnic disparities may affect the health or health care access of people with disabilities. OBJECTIVES: We examined potential disparities in overall health, insurance coverage status, and health service use between non-Hispanic whites, non-Hispanic blacks, and Hispanics, among a nationally representative US sample of adults with and without disabilities (N=63,257), using both bivariate and multivariate methods. We tested 2 definitions of disparity. RESULTS: Under the more conservative definition, we confirmed the presence of both racial and ethnic disparities in overall health, total annual health care visits, and the percentage reporting no doctor visit during the year among people with less severe disabilities; Hispanics also evidenced a disparity in rates uninsured relative to non-Hispanic whites in this group. Racial/ethnic disparities were less common among persons with more severe disabilities that affected activities of daily living or instrumental activities. CONCLUSIONS: We conclude that the reduction of disparities between the populations of people with and without disabilities will require specific attention to racial and ethnic disparities in health, insurance coverage, and service use.

Conceptualizing disability in US national surveys: application of the World Health Organization's (WHO) International Classification of Functioning, Disability, and Health (ICF) framework.

PURPOSE: Disability data inform resource allocation and utilization, characterize functioning and changes over time, and provide a mechanism to monitor progress toward promoting and protecting the rights of individuals with disability. Data collection efforts, however, define and measure disability in varied ways. Our objective was to see how the content of disability measures differed in five US national surveys and over time. METHODS: Using the WHO ICF as a conceptual framework for measuring disability, we assessed the National Health Interview Survey (NHIS), Current Population Survey (CPS), Survey of Income and Program Participation (SIPP), National Survey of SSI Children and Families (NSCF), and American Community Survey (ACS) for their content coverage of disability relative to each of the four ICF components (i.e., body functions, body structures, activities and participation, and environment). We used second-level ICF three-digit codes to classify question content into categories within each ICF component and computed the proportion of categories within each ICF component that was represented in the questions selected from these five surveys. RESULTS: The disability measures varied across surveys and years. The NHIS captured a greater proportion of the ICF body functions and body structures components than did other surveys. The SIPP captured the most content of the ICF activities and participation component, and the NSCF contained the most content of the ICF environmental factors component. CONCLUSIONS: This research successfully illustrated demonstrated the utility of the ICF in examining the content of disability measures in five national surveys and over time.

Transitions in mobility, ADLs, and IADLs among working-age Medicare beneficiaries.

BACKGROUND: Disability is a dynamic process where functional status may change over time. Examination of the Medicare population suggests that, for those over age 65, disability status will fluctuate in 30% of beneficiaries each year. Less is known about those under age 65. The dynamic nature of disability is of relevance since it has important implications for social policies related to disability. OBJECTIVES: To: (1) describe the characteristics of Medicare beneficiaries eligible due to disability; and (2) estimate the proportion of individuals with transitions in functional status over a one-year period stratified by baseline characteristics and diagnostic subgroups. METHODS: We used the Medicare Current Beneficiary Survey from 1995 to 2005 to examine transitions in mobility and daily activities among individuals who were eligible for Medicare coverage due to disability. RESULTS: From the standpoint of function in mobility and daily activities, the working-age Medicare population with disability is fairly stable. While 75%-90% of our sample reported no disability or stable disability from one year to the next, depending on the condition and disability metric, as many as 13-14% of individuals showed improvement or decline in their functional status. CONCLUSIONS: In the working-age population with disability, a small percentage of individuals will improve or worsen from one year to the next. Since these transitions are associated with a variety of individual characteristics including health conditions, further research applied to larger samples is required to refine policy relevant models that might inform decisions related to ongoing eligibility for disability programs.

Combining agreement and frequency rating scales to optimize psychometrics in measuring behavioral health functioning.

OBJECTIVE: The goal of this article was to investigate optimal functioning of using frequency vs. agreement rating scales in two subdomains of the newly developed Work Disability Functional Assessment Battery: the Mood & Emotions and Behavioral Control scales. STUDY DESIGN AND SETTING: A psychometric study comparing rating scale performance embedded in a cross-sectional survey used for developing a new instrument to measure behavioral health functioning among adults applying for disability benefits in the United States was performed. RESULTS: Within the sample of 1,017 respondents, the range of response category endorsement was similar for both frequency and agreement item types for both scales. There were fewer missing values in the frequency items than the agreement items. Both frequency and agreement items showed acceptable reliability. The frequency items demonstrated optimal effectiveness around the mean ± 1-2 standard deviation score range; the agreement items performed better at the extreme score ranges. CONCLUSION: Findings suggest an optimal response format requires a mix of both agreement-based and frequency-based items. Frequency items perform better in the normal range of responses, capturing specific behaviors, reactions, or situations that may elicit a specific response. Agreement items do better for those whose scores are more extreme and capture subjective content related to general attitudes, behaviors, or feelings of work-related behavioral health functioning.

Development of a computer-adaptive physical function instrument for Social Security Administration disability determination.

OBJECTIVES: To develop and test an instrument to assess physical function for Social Security Administration (SSA) disability programs, the SSA-Physical Function (SSA-PF) instrument. Item response theory (IRT) analyses were used to (1) create a calibrated item bank for each of the factors identified in prior factor analyses, (2) assess the fit of the items within each scale, (3) develop separate computer-adaptive testing (CAT) instruments for each scale, and (4) conduct initial psychometric testing. DESIGN: Cross-sectional data collection; IRT analyses; CAT simulation. SETTING: Telephone and Internet survey. PARTICIPANTS: Two samples: SSA claimants (n=1017) and adults from the U.S. general population (n=999). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Model fit statistics, correlation, and reliability coefficients. RESULTS: IRT analyses resulted in 5 unidimensional SSA-PF scales: Changing & Maintaining Body Position, Whole Body Mobility, Upper Body Function, Upper Extremity Fine Motor, and Wheelchair Mobility for a total of 102 items. High CAT accuracy was demonstrated by strong correlations between simulated CAT scores and those from the full item banks. On comparing the simulated CATs with the full item banks, very little loss of reliability or precision was noted, except at the lower and upper ranges of each scale. No difference in response patterns by age or sex was noted. The distributions of claimant scores were shifted to the lower end of each scale compared with those of a sample of U.S. adults. CONCLUSIONS: The SSA-PF instrument contributes important new methodology for measuring the physical function of adults applying to the SSA disability programs. Initial evaluation revealed that the SSA-PF instrument achieved considerable breadth of coverage in each content domain and demonstrated noteworthy psychometric properties.

Development of an instrument to measure behavioral health function for work disability: item pool construction and factor analysis.

OBJECTIVES: To develop a broad set of claimant-reported items to assess behavioral health functioning relevant to the Social Security disability determination processes, and to evaluate the underlying structure of behavioral health functioning for use in development of a new functional assessment instrument. DESIGN: Cross-sectional. SETTING: Community. PARTICIPANTS: Item pools of behavioral health functioning were developed, refined, and field tested in a sample of persons applying for Social Security disability benefits (N=1015) who reported difficulties working because of mental or both mental and physical conditions. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Social Security Administration Behavioral Health (SSA-BH) measurement instrument. RESULTS: Confirmatory factor analysis (CFA) specified that a 4-factor model (self-efficacy, mood and emotions, behavioral control, social interactions) had the optimal fit with the data and was also consistent with our hypothesized conceptual framework for characterizing behavioral health functioning. When the items within each of the 4 scales were tested in CFA, the fit statistics indicated adequate support for characterizing behavioral health as a unidimensional construct along these 4 distinct scales of function. CONCLUSIONS: This work represents a significant advance both conceptually and psychometrically in assessment methodologies for work-related behavioral health. The measurement of behavioral health functioning relevant to the context of work requires the assessment of multiple dimensions of behavioral health functioning. Specifically, we identified a 4-factor model solution that represented key domains of work-related behavioral health functioning. These results guided the development and scale formation of a new SSA-BH instrument.

Conceptual foundation for measures of physical function and behavioral health function for Social Security work disability evaluation.

Physical and mental impairments represent the 2 largest health condition categories for which workers receive Social Security disability benefits. Comprehensive assessment of physical and mental impairments should include aspects beyond medical conditions such as a person's underlying capabilities as well as activity demands relevant to the context of work. The objective of this article is to describe the initial conceptual stages of developing new measurement instruments of behavioral health and physical functioning relevant for Social Security work disability evaluation purposes. To outline a clear conceptualization of the constructs to be measured, 2 content models were developed using structured and informal qualitative approaches. We performed a structured literature review focusing on work disability and incorporating aspects of the International Classification of Functioning, Disability and Health as a unifying taxonomy for framework development. Expert interviews provided advice and consultation to enhance face validity of the resulting content models. The content model for work-related behavioral health function identifies 5 major domains: (1) behavior control, (2) basic interactions, (3) temperament and personality, (4) adaptability, and (5) workplace behaviors. The content model describing physical functioning includes 3 domains: (1) changing and maintaining body position, (2) whole-body mobility, and (3) carrying, moving, and handling objects. These content models informed subsequent measurement properties including item development and measurement scale construction, and provided conceptual coherence guiding future empirical inquiry. The proposed measurement approaches show promise to comprehensively and systematically assess physical and behavioral health functioning relevant to work.

Development of a self-report physical function instrument for disability assessment: item pool construction and factor analysis.

OBJECTIVES: To build a comprehensive item pool representing work-relevant physical functioning and to test the factor structure of the item pool. These developmental steps represent initial outcomes of a broader project to develop instruments for the assessment of function within the context of Social Security Administration (SSA) disability programs. DESIGN: Comprehensive literature review; gap analysis; item generation with expert panel input; stakeholder interviews; cognitive interviews; cross-sectional survey administration; and exploratory and confirmatory factor analyses to assess item pool structure. SETTING: In-person and semistructured interviews and Internet and telephone surveys. PARTICIPANTS: Sample of SSA claimants (n=1017) and a normative sample of adults from the U.S. general population (n=999). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Model fit statistics. RESULTS: The final item pool consisted of 139 items. Within the claimant sample, 58.7% were white; 31.8% were black; 46.6% were women; and the mean age was 49.7 years. Initial factor analyses revealed a 4-factor solution, which included more items and allowed separate characterization of: (1) changing and maintaining body position, (2) whole body mobility, (3) upper body function, and (4) upper extremity fine motor. The final 4-factor model included 91 items. Confirmatory factor analyses for the 4-factor models for the claimant and the normative samples demonstrated very good fit. Fit statistics for claimant and normative samples, respectively, were: Comparative Fit Index=.93 and .98; Tucker-Lewis Index=.92 and .98; and root mean square error approximation=.05 and .04. CONCLUSIONS: The factor structure of the physical function item pool closely resembled the hypothesized content model. The 4 scales relevant to work activities offer promise for providing reliable information about claimant physical functioning relevant to work disability.