Version May 2024
INTRODUCTION — Disability evaluation is an important aspect of clinical care. Accurate evaluation significantly affects the wellbeing of both patients and society, given the impact of disability status on financial remuneration, return to work, personal and workplace productivity, and access for existing and future health care needs.
Both treating and consulting clinicians are often asked to evaluate their patients for disability. Input from treating clinicians is crucial to disability evaluation because they often have the most in-depth and longitudinal knowledge of the patient's conditions and function, may be aware of medical and psychosocial contributions to ongoing disability, and can best advise on severity, permanency, and possible accommodations needed for an impairment.
When treating clinicians are unable to provide a disability evaluation, or when an insurance carrier has concerns that the treating clinician cannot be impartial, a consulting clinician may be hired to provide an opinion as an "independent" medical examiner. There is no doctor-patient relationship between the independent medical examiner and the patient.
Assessment of disability is complex, variable, and challenging even among clinicians experienced in disability determination. A number of factors give rise to these challenges [1]:
●The determination of disability requires a synthesis of clinical and nonclinical information.
●The definition of disability is not standardized across agencies that request a disability assessment.
●The clinician is often required to define limitations in functional abilities and provide medical judgment for legal interpretation when medical evidence is insufficient.
●The skills necessary to interact with multiple administrative and legal entities are not usually taught during medical training.
●Disability determination usually has financial implications for the individual and society that treating clinicians often consider.
●Treating clinicians may feel uncomfortable making a determination which is not consistent with their patient's preference and could adversely impact the doctor-patient relationship.
●Limited time availability in treatment medical encounters can magnify these concerns.
This topic will discuss definitions of impairment and disability as well as review the clinician's role and important considerations when performing a disability assessment. Issues related to specific occupational disorders are discussed separately. (See "Occupational low back pain: Evaluation and management" and "Evaluation of pulmonary disability".)
CLINICIAN ROLE — The role of the clinician is to assess and document medical impairment and functional abilities in accord with the requirements of the requesting agency. Clinicians will most commonly be asked to complete disability evaluation for the Social Security Administration (SSA), Workers' Compensation, or a private agency. Some agencies require the clinician to discuss the degree of disability and work abilities. This documentation is interpreted and used by the judicial system, state and federal agencies, and private insurance companies to determine the degree of disability and resulting compensation.
The clinician is often asked to:
●Define and document findings related to the individual's medical problems or impairments
●Define the severity of the medical problem (eg, temporary or permanent, partial or total impairment)
●Identify functional limitations and restrictions associated with impairments
●Synthesize medical information from different sources into a coherent picture of the individual's medical conditions and functional ability, which may include evaluation of work capability
Most agencies recognize that treating clinicians can provide the best evidence for the existence of medical impairments and their consequences. While medical training may not specifically prepare clinicians to assess functional limitations, clinicians in practice have the unique opportunity to observe the effects of physical and mental impairments on their patients' overall function, including the ability to work and live independently. SSA regulations note that treating medical professionals, with their longitudinal patient experience, can provide a perspective not obtainable from medical findings alone or from independent examinations [2,3].
The first step in disability evaluation is the determination of medical impairment and its impact on the ability to perform activities of daily living, which can help in determining functional abilities and limitations. An assessment of a patient's ability to perform work-related tasks for a particular occupation may or may not be required as part of the disability evaluation.
DEFINITIONS — Impairment is a disorder that causes alteration of body structure or function. Disability, commonly confused with impairment, refers to the limitation, due to impairment, in the ability to perform activities of daily living or complex activities such as work. Impairment is not defined relative to an environment. By contrast, disability accounts for the ability of an individual with an impairment to function in a specific environment. As an example, impairment due to a herniated disc with intermittent radiculopathy is present whether an individual is at home or at work. However, an individual with degenerative disc disease and sciatica is likely to be disabled for work as a manual laborer but may have minimal or no disability as a dispatch agent or while functioning at home.
Impairment — Definitions of medical impairment vary, but common to all is the concept of a disorder that causes alteration of body structure or function and specifically loss of functional use. Supportive clinical signs and/or laboratory findings are typically needed to document specific impairments and severity, with objective findings weighed more heavily in decision-making than subjective complaints. In 2017, SSA revised the definition of objective medical evidence to clarify that it means signs, laboratory findings, or both. Per the SSA, although all evidence is considered, an impairment cannot be based on a diagnosis, symptoms, or a medical opinion. Psychological diagnoses are usually included [4-7]. Commonly used definitions of impairment and disability are shown in a table (table 1).
The American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment, first published in 1958, promote a standardized approach to the assessment of medical impairment, especially for use in workers' compensation [4,5,8]. Many states' legal statutes, codes, or regulations in workers' compensation, personal injury, or disability law have adopted various portions or editions of these guides to define diagnostic criteria required for medical impairment (table 2) [7,9].
Most agencies consider an impairment permanent and stationary, or at maximal medical improvement (MMI), if there is no significant improvement seen or expected in the condition for a 12-month interval. Changes in the condition and stability versus progression should be documented. Fluctuations in the natural history of the condition (eg, variable glucose levels in a diabetic patient) would still be categorized as a stationary status or at MMI. Progression and greater impairment would be noted if the individual's diabetes progressed to involve renal dysfunction or if a disc herniation led to objective motor loss.
Disability — The SSA defines disability as "the inability to engage in any substantial, gainful activity by reason of a medically-determinable physical or mental impairment(s), which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months" [2,10].
Models of disability distinguish impairment, function, and disability [11]. These models acknowledge that disability is not inherent in the individual but results from the interaction between the impaired individual and the environment in which they function. The presence or absence of accommodations at work or home significantly determine whether the individual has a disability in a given setting.
Clinicians contribute to the determination of disability through their assessment of impairment and its impact on the individual's ability to perform activities of daily living and work. Disability assessment, commonly decided by other parties (insurers) or agencies (SSA), requires consideration of additional factors such as age, education, prior work history, and future employability [11,12].
Definitions of disability from leading agencies vary (table 1). Definitions commonly convey that disability incorporates the interaction of an impairment with its functional impact on a person's ability to participate in a life situation or activity.
The World Health Organization (WHO) identifies work disability as the result of the interaction of an individual's impairments and functional limitations in the context of multiple other factors, including [6]:
●Access to assistive technologies
●Attitudinal and other personal characteristics (eg, age, education, skills, and work history)
●Physical and mental requirements of potential jobs
●Transportation accessibility
●Attitudes of family members and coworkers
●Willingness of an employer to make accommodations
Many agencies, including the SSA, do not have the resources to implement the extensive evaluation required to assess disability as specified by the WHO. In lieu of this, screening criteria or equivalents are typically developed. Some agencies and states use impairment as a proxy for disability [11,13].
EPIDEMIOLOGY
Disability — In the United States in 2021, rates of noninstitutionalized adults reporting at least one disability range from 13 to 27 [14-16]
Disability in mobility, independent living, and cognition were most frequently reported (5 percent). Data from the 2009 to 2012 National Health Interview Survey found that 11.6 percent of United States adults 18 to 64 years of age reported a disability (defined as serious difficulty with hearing, vision, cognitive ability, or mobility [walking or climbing stairs]) [17].
Rates of disability vary by race and ethnicity [12,18]. Rates of disability also increase with age; 35.5 percent of individuals ≥65 years report disability, compared with 15.7 percent of individuals 18 to 44 years [19]. The aging population is increasing, with projected doubling of individuals who are aged 65 years and older between 2000 and 2030.
The top three conditions causing self-reported disability were arthritis, back or spine problems, and heart conditions [20-22]. Compared with earlier surveys, rates of musculoskeletal conditions as a cause of disability increased, and heart disease as a disability cause decreased. Coronavirus disease (COVID-19) likely resulted in an increase of disabled people within and outside the workforce [23]. An increase of more than 1.5 million working-age individuals reported a disability since mid-2020, attributed to COVID-19, however, those counts have been declining consistent with some individuals reporting recovery [24].
Among adults reporting a disability, the most commonly identified limitations were difficulty walking three city blocks (10.3 percent) and climbing a flight of stairs (10.0 percent) [22]. About 14 percent of noninstitutionalized people experience "complex activity limitations" and report an inability to participate fully in social roles, maintain a household, work, pursue hobbies, visit friends, and go to the movies or sporting events [21]. Trends in aging and disability in the United States are available on the American Society on Aging website [25].
Given these projections and the increased prevalence of disability among the United States population, policy makers and workplaces need to identify and meet the health and social needs of the expanding population of people with disabilities [11,21].
Work-related injury and disability — Workplace health and disability reflect overall population health. Rates of occupational injuries, illness, and fatalities have been declining in the United States. In 2020 to 2021, the Bureau of Labor Statistics reported 2.7 cases per 100 full-time equivalent (FTE) workers of nonfatal occupational injuries and illness in the private sector [26].
The COVID-19 pandemic in 2020 resulted in greater workplace hazards for workers in the healthcare and social assistance industry sector, with increases in nonfatal occupational injuries and illnesses [27].
In 2021, there was an 8.9 percent increase in fatal work injuries in the United States from 2020, and the fatal work injury rate was 3.6 fatalities per 100,000 full-time equivalent (FTE) workers [28]. Worker fatalities due to exposure to harmful substances or environments also increased in 2021 [28]. Highest-risk industries for occupational fatalities include agriculture, forestry, fishing, hunting, transportation, warehousing, and construction [29,30].
Economic impact — The economic burden of increasing disability in society varies widely by state, as does the prevalence of diseases, injuries, and risk factors [31].
In January 2023, 7.6 million people received disabled-worker benefits from the SSA. Payments also went to some of their family members: 90,000 spouses and 1.1 million children [31].
DISABILITY ASSESSMENT — In the United States, systems that commonly require information from the clinician to determine disability include the Social Security Disability System, Workers' Compensation, Railroad Retirement, and Civil Service programs. Two of the most important sources of assistance for Americans with disabilities are Supplemental Security Income (SSI) and Social Security Disability Insurance (SSDI), both administered by the SSA. SSI and SSDI act as a safety net for persons with disabilities, providing both cash assistance (monthly checks) and eligibility for health insurance (Medicaid and/or Medicare).
Federal, state, and private programs require medical input, typically at the initial evaluation stage and often at later stages of adjudication, for disability determination. Most often, agencies request treating clinicians to document the medical impairment and provide a medical judgment regarding functional limitations from the impairment. This functional assessment may include the ability to perform specific work activities, as requested by the SSA, the state and federal workers' compensation systems, and specific employee groups covered by the Long Shore and Harbor Workers' Compensation Act (LHWCA). Insurance carriers or patients' attorneys may arrange private disability assessments, normally performed by clinicians, who are designated as "independent medical evaluators."
Clinicians and agencies often presume a strong correlation between the presence of a severe impairment and inability to work, with severe impairment used as a proxy for disability. This assumption is often satisfactory with severe impairments such as advanced cancer and reduced lung function or cardiac ejection fraction. For more moderate impairments, determining the patient's functional abilities and limitations will enable the agency disability evaluator to weigh those abilities in the context of the patient's education and work potential to determine if they are truly disabled from any work. Based upon information provided by the clinician, the disability evaluator considers whether a potential accommodation would be feasible, or whether the individual can realistically be retrained before determining if they are disabled from the essential or usual requirements of a specific job or the labor market. As an example, if the clinician provides information on the functional abilities of an individual who has had a myocardial infarction with atrial fibrillation, with an analysis of metabolic equivalents (METS), the evaluator can more objectively determine if they are totally disabled from specific manual labor or if they require restriction to sedentary or desk work.
For severely impaired individuals, using impairment as a surrogate for work disability does provide a practical method of evaluation to determine who is disabled from work. The clinician's assessment, especially when based upon objective findings or data, is of significant assistance in providing answers to the more complex and common questions of the patient's current and predicted functional abilities on a routine basis under usual work conditions [32]. The SSA and other agencies have the challenge of using this information along with the patient's age, education, and considerations of the increasingly complex and competitive labor market to determine a patient's ability to return to the labor force.
Social Security Administration — The clinician's role within the SSA system is to provide medical evidence about the nature and severity of an individual's impairment(s) and their functional abilities and limitations. The determination of disability is made by SSA.
The SSA asks the clinician to initially determine if the applicant has a severe impairment based upon objective medical evidence. An impairment is considered "severe" if it significantly interferes with an individual's ability to perform basic activities of daily living that are also needed in the workplace. These activities include walking, standing, sitting, lifting, pushing, pulling, reaching, carrying, handling, seeing, hearing, speaking, understanding, carrying out and remembering simple instructions, using judgment, responding appropriately (to supervision, coworkers, and usual work situations), and/or dealing with changes in a routine work setting.
If the impairment is severe and meets the listings discussed below (see 'Listing of impairments' below) and the patient is not working, they will likely be found to be disabled from any work. If the listing criteria are not met, the patient is not necessarily foreclosed from benefits, but further analysis of medical and vocational capabilities is then required.
In 2017, the SSA recognized Advanced Practice Registered Nurses (APRN), audiologists, and physician assistants (PA), along with clinicians, as acceptable medical sources who can provide the SSA with objective medical evidence for claims [33].
Listing of impairments — The SSA has two "Guides" for disability evaluation for clinicians: a Blue Book for treating clinicians and a Green Book for consulting clinicians, both available electronically [2,3]. The Blue Book explains the SSA disability process and provides a "Listing of Impairments" that clinicians can use to identify obviously disabled applicants who don't require the full evaluation process because their medical conditions meet criteria of sufficient severity [2]. The SSA listing of impairments can be found on their website.
The Listings are divided into 14 broad categories by organ system or disease type (eg, malignant neoplasm) and then subdivided by specific conditions. Each listing specifies clinical criteria or measures of functional limitation (eg, treadmill tests, pulmonary function test, range of motion of joints, or IQ tests) and duration of involvement. The Listings are not measures of disability but measures of the severity of impairment; when the impairments are severe, they serve as a proxy for total work disability [2,3,34].
The SSA has developed guidelines to address COVID-19 disability determination [35]. COVID -19 does not itself result in a listed disability condition but can be part of a combination of impairments, given its effects on respiratory, cardiovascular, renal, neurologic, and other body systems. [36].
If an applicant meets criteria for the medical diagnosis and findings on this list, and if the listed impairment has lasted or is expected to last at least 12 months or result in death, the applicant will meet the medical criteria for disability. For example, an applicant with a left ventricular ejection fraction of 30 percent or less who is unable to perform at a workload equivalent of 5 METS or less on an exercise test without exhibiting specified signs or symptoms (eg, electrocardiogram abnormalities or chest pain, Listing 4.02) is considered disabled according to the SSA. Some severe impairments are based on a diagnosis alone, such as amyotrophic lateral sclerosis (Listing 11.00) or inoperable malignancies (eg, Listing 13.09, metastatic melanoma) [3,11,34].
It is important that the clinician document all the elements in the listing. Incomplete documentation will lead to a rejected claim and need for resubmission and appeal, resulting in costly delays for the applicant and system.
If the medical condition fails to meet requirements for severity based upon the criteria for a single condition, the applicant may still meet disability criteria if the functional limitations of the impairment(s) are equal in severity and duration to the requirements of a listing. A combination of impairments of at least equal medical significance to those of a listed impairment is referred to as "medical equivalence." The clinician will need to provide detailed information on functional limitations as well as the severity and duration of the impairment, and provide an opinion regarding its equivalency to a particular listing. Supportability by objective medical evidence and consistency among medical opinions are given greater weight than unsupported opinion [33]. The SSA compares the applicant's medical impairments and functional limitations with those of a listing.
Usually, the local SSA first requests information from the treating clinician. If that evidence is unavailable or insufficient to make a determination, the SSA staff will arrange for a Consultative Examination in order to obtain the additional information needed [37].
Residual functional capacity — Applicants who do not have a listed impairment or equivalent conditions may qualify for SSA if the clinician identifies them as having reduced residual functional capacity (RFC), preventing them from performing their past work or any substantial gainful activity. The SSA takes into account the patient's age, education, and work experience in this determination. RFC is defined as the maximal activity an individual is able to perform despite functional limitations resulting from all impairments.
The following information will significantly assist the SSA in determining the RFC:
●How many hours during an eight-hour work day can the individual sit, stand, or walk?
●How many pounds can the individual lift frequently (about two-thirds of a workday) and occasionally (about one-third of the workday)?
According to the SSA, RFC assessment may be based solely on medical evidence if sufficient objective findings (eg, signs, laboratory and diagnostic findings) are provided to assess the applicant's capacity for work-related functions. These functions may include standing, lifting, carrying, and handling (which can be translated into functional capacity for sedentary, light, medium, heavy, or very heavy work); mental demands, such as making judgments and tolerating job-related stress; and sensory requirements, such as hearing and seeing [2,3].
To assess RFC, the clinician can use objective medical evidence (eg, pulmonary function, cardiac output, hearing, or vision studies) and clinical judgment based upon their knowledge of the patient. The clinician can also assess the patient's functional abilities and limitations in daily activities, review reports from other practitioners (eg, physical therapist), and/or order a functional capacity evaluation. Patients should not be cleared to do work activities that could worsen their condition, such as heavy lifting following a discectomy. Discussion with specialists who performed a procedure to address current and future functional limitations is often helpful.
For example, an individual who completed physical therapy for a rotator cuff repair and lifts their grandchild and carries groceries or laundry is able to perform some lifting. To identify their functional abilities and limitations, it can be helpful to ask the patient to describe a typical day and assess the scope of their activities of daily living. Asking patients how long they can drive and do errands, how long they watch TV, or what movies they have seen recently may give estimates regarding their ability to sit. Whether they drove independently to the examination and their observed function prior to and during the assessment can assist with impairment determination. Comparing their measured range of motion with a review of relevant studies and published reports on the required range of motion needed to perform activities daily also helps to estimate functional ability [38-40].
The SSA uses medical and vocational "grids" which identify different levels of exertional capacity (sedentary, light, medium, heavy, or very heavy) required for applicants able to work based upon age, education, and prior work experience [41]. In general, sedentary work requires the ability to sit for six hours, to stand/walk for two, and to lift no more than 10 pounds at a time. Light and medium work require the ability to stand/walk for six hours and to lift no more than 20 or 50 pounds, respectively [34].
Documentation — Providing thorough medical documentation at the initiation of the claim will expedite the assessment and conserve SSA resources in claim evaluation. Clinicians may be asked to write a letter or to complete a form documenting findings for an SSA disability claim. The report should include the history and clinical and laboratory findings, as well as the diagnosis and treatment prescribed and the response to treatment. It should also include a statement about what work activities the patient can still do despite their impairment.
A sample report is listed in the figure, which includes helpful and required criteria listed below (figure 1) [2,3,34]:
●Your relationship (treating or consulting clinician) with the patient and length of the relationship.
●Summary of the most recent medical evaluation, at a minimum including diagnostically positive or negative findings. The clinician should attach a copy of the medical record to document continuity of treatment and indicate that "the medical records are attached to this report."
●A list of impairments or diagnoses, with a comparison to the SSA Listing of Impairments. Identify which patient's findings match the SSA criteria for that impairment.
●If criteria for a listed impairment are not met, include details of the patient's functional limitations as a synthesis of individual impairments, the expected duration of the limitations, and assessment of the patient's ability to perform basic work activities.
●An opinion indicating which listing was met, or how the listings are equaled, accounting for the functional limitations.
●An assessment of functional restrictions. As an example, "This patient should not sit for prolonged periods (no more than one-half hour at a time), should not stand for more than 15 minutes continuously, and should not lift or carry more than 10 pounds. They should not participate in activities that require stooping, bending, crawling, or climbing."
●Attachment of all relevant notes and clinical studies.
The clinician states the patient's limitations and abilities; the SSA makes the determination regarding disability. A letter will not be supportive of a claim if it indicates the patient has few limitations.
DISABILITY ASSESSMENT TOOLS — Work disability is most reliably assessed through knowledge of the medical condition and its associated limitations, knowledge of the job and workplace environment, and an assessment of the individual's specific functional abilities. The assessment is typically based upon the medical evaluation; information obtained from tests, such as a functional capacity evaluation, and validated questionnaires are sometimes included. Validated measurements are being developed to meet the need for highly reproducible, sensitive, and low-cost assessments to reliably classify applicants abilities. Knowledge of functional abilities and limitations are required to assess work capabilities [32].
Questionnaires — Many validated questionnaires have been developed for research and clinical use to enhance objectivity in the assessment of functional and pain-related impairment. These tools, often condition-specific (eg, cognition, arthritis), can be useful adjuncts to the clinician's medical judgment.
●PROMIS – Patient-Reported Outcomes Measurement Information System (PROMIS), developed by the National Institutes of Health (NIH) and six primary research sites in 2004, has as its mission the creation of a state-of-the-art assessment system for self-reported health for use in both clinical research and practice. Reviewing about 8000 instruments, PROMIS investigators have identified key items in five domains (physical function, pain, fatigue, emotional distress, and social support) which assess health and function [42,43].
PROMIS provides assessments which assess function in multiple formats: short forms, fixed sets of 4 to 10 items or questions for one domain; profiles, which are fixed collections of short forms from multiple domains; and computer adaptive testing (CAT), in which items are dynamically selected for administration from an item bank based upon the respondent's previous answers [44].
A comparative study between the PROMIS questionnaire and other traditional instruments to assess rheumatic diseases demonstrated that PROMIS outperformed traditional legacy questionnaires. Comparison of other standard questionnaires with PROMIS questionnaires are underway in dozens of domains with positive findings regarding the improved accuracy of PROMIS items and questions [42]. PROMIS is focused on ways to better quantify patient-reported symptoms, such as pain and fatigue, and other aspects of health-related quality of life and function across a wide variety of chronic diseases and conditions.
PROMIS can be used on a computer or via a paper-and-pencil version; the results can be compared with population norms and shared with the patient at point of care.
●Computer-based questionnaires – CAT selects the best questions to sharpen the estimate of a person's functional ability, based on prior responses to earlier questions.
Advances in efficient and accurate assessment of functional ability and disability are based on ongoing research in item response theory or CAT, leading to the development of functional testing instruments. Such instruments score self-reported responses to functional questions (eg, how much difficulty an individual has lifting a carton of milk) followed by a new question based upon the initial response (eg, how much difficulty do they have lifting a suitcase).
Artificial intelligence is used to select subsequent questions based upon prior answers until a set level of precision and high degree of accuracy is reached to relate responses to functional ability [45]. CAT modules addressing multiple conditions and symptoms are available for the clinician to use on a secure platform, without charge, on the Health Measures website. The SSA and the Rehabilitation Medicine Department of the NIH are supporting this landmark work in CAT [46].
●Traditional questionnaires
•Musculoskeletal assessment instruments – Both the American Academy of Orthopedics and the American Academy of Physical Medicine and Rehabilitation (AAPMR) [47] have questionnaires to assist with condition specific (eg, osteoarthritis) and body part (cervical spine) disability evaluation [48]. The AAPMR had detailed guidance on assessment and management on COVID-19-related disability [49].
More than 10 validated low-back functional assessment questionnaires are in common use for clinicians to assess function and pain among patients with chronic back pain [50-59]. Among the most commonly used include the Oswestry Disability Questionnaire (figure 2), which assesses pain and more complex activities, and the Short Form 36 (SF-36), which evaluates general health perceptions along with physical, social, and emotional functioning [60,61]. For the clinician who sees a particular condition commonly, it would be best to research the sensitivity and specificity of the scale for a particular disorder. For example, the Roland Morris Disability Questionnaire (RMDQ) is especially robust for patients with post lumbar disc surgery [62]. The most commonly used functional outcomes for chronic low back pain include the Oswestry Disability Index, Roland Morris Disability Index, and range of motion [59].
One study compared the modified Oswestry Disability Questionnaire, the Quebec Back Pain Disability Scale (form 1), the Roland-Morris Disability Questionnaire, the Waddell Disability Index, and the physical health scales of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) for reliability and responsiveness [63]. Measurements obtained with the modified Oswestry Disability Questionnaire, the Quebec Back Pain Disability Scale, and the SF-36 Physical Functioning scale were the most reliable and had sufficient width scale to reliably detect improvement or worsening in most patients.
There are multiple validated upper-extremity functional assessment questionnaires available for clinicians and other health providers, based upon patient-reported or clinical outcome measures [64-67]. The Disability of the Shoulder, Arm, and Hand (DASH) Questionnaire, SF-36 Health Survey Questionnaire, and the Health Assessment Questionnaire are commonly used patient reported outcome measures [67].
Lower-extremity assessment tools for the clinician in assessment of lower limb function include the American Academy of Orthopedic Surgeons lower limb questionnaire [68] and the Lower-Limb Tasks Questionnaire [69].
•Pain disability assessment instruments – Pain disability assessment instruments may be used as a supplement to a functional body part questionnaire when chronic pain is the major limitation to function. Pain behavior, interference, and intensity can be measured by different instruments through PROMIS. The Pain Disability Index is available online [70], and there are additional commonly used pain questionnaires (table 3) [59,71-74].
Functional capacity evaluation — The functional capacity evaluation (FCE) is a systematic, comprehensive, and relatively objective measurement of maximum work ability [75]. Its purpose is to assess a patient's safe functional abilities compared with the physical demands of job-specific work.
A functional capacity evaluation is typically administered by a physical or occupational therapist. A submaximal effort on the individual's part will severely limit the results.
There is considerable variability in the tests used in FCE. Tests vary in validity, reliability, and ability to predict return to work. Physical or occupational therapy providers may be helpful in recommendations for an FCE, since tests vary in their ability to accurately assess different physical performance [76]. Clinicians who wish to assess functional ability without referral for physical testing may use the Roland Morris Disability Questionnaire (RMDQ), which is relatively quick and has demonstrated validity for measuring functional status [77].
WORKERS' COMPENSATION — The goal of workers' compensation programs is to provide prompt and appropriate medical treatment and, when appropriate, financial benefits to injured workers with the goal of restoring their function to their preinjury state while limiting employers' liabilities.
Under workers' compensation, employees are spared lengthy and uncertain litigation, while employers can expect more predictable costs than under the law of negligence. Additionally, employers have an incentive to improve workplace safety given their responsibility for medical and associated costs. Workers' compensation law varies among states. Common to all state systems are that employers pay all related medical costs, either directly or through insurance; injured workers receive partial income replacement and medical care for injury; and dependents, in case of worker death, receive income and burial benefits. The income benefit for disability is set at a specified fraction of the worker's usual earnings for as long as they are unable to return to work, or for a set period of time as provided by the state's workers compensation law. In most states, benefits are payable only for defined periods of time.
Cases of occupationally caused disease are treated differently than those involving traumatic injury and are more often disputed as work-related, given their multifactorial nature and the long latency of many occupational diseases. All injuries or occupational diseases deemed compensable must "arise out of" or occur "in the course of" or "have been triggered by" employment, even if manifest and detected years later.
OSHA has published guidelines to determine whether a COVID-19 illness is work related [78]. However, given the potential for exposure within and outside of work, it can be difficult to determine whether a coronavirus illness is work-related. OSHA's guidance emphasizes that employers must make reasonable efforts, to ascertain whether a particular case of coronavirus is work-related [79].
In some states in the United States, COVID-19-related illness and deaths among essential workers are being considered occupational due to presumed work exposure, although states vary in their definition of essential worker and which groups of such workers are considered to have contracted COVID-19 from work [80]. Some states are determining the likelihood of COVID-19 being contracted at work on a case-by-case basis, requesting a higher level of proof (eg, if not for their job, would the worker have been exposed to the virus or contracted the disease). Essential workers with disabilities due to COVID-19 are evaluated on the basis of state regulations.
Evaluation of an injured worker — Evaluation for workers' compensation has some fundamental similarities to the SSA disability evaluation. The initial step for workers' compensation evaluations is impairment assessment. Clinicians commonly are asked to also evaluate work-related disability for agencies outside of the SSA.
In the case of an undisputed work-related injury, the clinician is commonly asked to document the degree of impairment, functional limitations, duration of limitation (temporary or permanent), the degree of disability (partial or total), and the ability to return to work (with or without restrictions). As an example, an assessment of a right-hand dominant worker who developed right-sided carpal tunnel syndrome in the course of work might appear as follows:
●Impairment – Right carpal tunnel syndrome.
●Functional limitation – Inability to bend the right wrist repeatedly, or perform repetitive finger use associated with high force, long duration, and extremes of wrist motion and vibration. Keep the wrists straight, in a neutral position, as much as possible. Minimize repetitive, strong grasping or pinching objects with the thumb. Take frequent hand and wrist breaks.
●Duration of disability – Temporary pending surgical evaluation.
●Disability – Disabled from any work requiring repetitive finger use associated with high force, long duration, and extremes of wrist motion and vibration in the dominant hand.
In the case of a right-handed machine operator with repetitive hand use, this would likely constitute total work disability but might result in no disability for a telephone operator who works with a headset and does not need to use their hands for repetitive activity.
If the worker were thought to have a permanent impairment, the clinician would be asked to assess the permanent functional loss. This is commonly a percentage of the body part or whole person function, referred to as an impairment rating. The American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment ("Guides") developed impairment percentages to reflect the impact of the impairment on the ability to perform activities of daily living [8]. Some states use the AMA Guides percentage of permanent impairment as a direct proxy for disability and award monetary settlements for permanent loss directly from those percentages, although the Guides specifically discourage this practice [4,8]. Other states use these percentages of impairment as one component of an assessment, also considering factors including vocation, age, and education before determining a disability award. Some states, such as New York, have used their own guidelines to evaluate the extent of loss of use for extremities or sense organs, referred to as a "schedule loss of use."
The Guides can serve as a useful and, in some states, required reference for clinicians to use in their evaluation and documentation of permanent impairment and its contribution to disability. However, the Guides have significant limitations:
●They do not directly estimate work disability.
●Medical criteria are not solely evidence-based.
●Impairment percentage ratings are consensus-based and have varied over time, with decreased impairment ratings being the general trend, given increased overall health care costs [8].
Role of the clinician — The role of the clinician in workers' compensation is to fulfill their state's requirements for evaluating and treating an injured worker. The clinician can usually download required criteria and forms from their state's workers' compensation website. Some states require the clinician be authorized or credentialed by the state's workers' compensation board in order to evaluate workers' compensation patients. Some edition of the AMA's Guides is used by 32 states in workers' compensation, with 15 additional states allowing the use of these Guides [81].
The workers' compensation process usually requires the clinician to perform the following steps:
●Identify the particular state or federal workers' compensation regulation in effect. The appropriate workers' compensation guideline is based upon the employer and the employee location at the time of the work-related injury or illness. Federal employees are covered under the Federal Employment Compensation Act. Most injured nonfederal workers are covered under their state workers' compensation legislation. However, railroad workers engaged in interstate commerce are covered under the Federal Employment Liability Act (FELA) and miners suffering from "black lung" (coal workers' pneumoconiosis) are covered under the Black Lung Benefits Act. Often, police and firefighters may be covered under separate workers' compensation regulations, with certain diseases being more readily accepted as occupational, since both the exposure and a causal associations between the anticipated occupational exposures and disease are presumed.
●Evaluate the individual worker's medical impairments and functional abilities based upon the jurisdiction or state requirements. States may require that the clinician use a particular edition of the AMA Guides (table 2).
●If requested, assess disability, checking whether the clinician is required to use the state workers' compensation board guidelines or can use their choice of validated disability assessment tools. (See 'Disability assessment tools' above.)
●To determine if the patient can perform a particular job, request that the employer provide the essential functions of the job or the specific job description. If one is unavailable or irrelevant, use the O*NvET system [82], a key source for comprehensive occupational information regarding occupations and their included tasks, skills, work activities, and work context. Other sources include the Dictionary of Occupational Titles [83].
●Assess and document whether the worker has the functional ability to meet the essential requirements of their occupation without harm to themselves or others, or if the essential job responsibilities can be performed with a reasonable workplace accommodation. For example, does an injured worker have sufficient cardiac reserve to safely do moderate physical work as defined by a recent stress test? If not, the clinician can request a reasonable accommodation be made to incorporate a lower level of physical ability. An injured worker who can currently do only occasional overhead work following shoulder surgery may be able to return to work with accommodations. The employer is responsible for evaluating and meeting a request for workplace accommodation.
●Clinicians may also be asked to comment on whether a patient has the medical ability to do other types of work in lieu of their usual customary work. This requires the clinicians to express an opinion on residual functional capacity but not on specific alternative jobs. As an example, a clinician might state that a patient could not do their usual work of frequent lifting >25 lbs and bending as a licensed practical nurse, and that their functional capacity is limited to sedentary work as described by state guidelines. The clinician should not specifically state that the patient could work as a receptionist; the determination of whether there are other jobs for the patient is an administrative question best addressed by a vocational expert.
SUMMARY
●The role of the clinician – The role of the clinician in disability evaluation is to define and document findings related to the individual's medical problems and associated functional limitations and to collate information from different sources into a coherent picture of the individual's medical conditions and functional ability. Many agencies, like the SSA, recognize that treating clinicians can provide the best evidence for the existence of medical impairments and their consequences. (See 'Clinician role' above.)
●Determining impairment – The first step in disability evaluation is the determination of medical impairment and its impact on the ability to perform activities of daily living. Impairment has been defined as loss of use or derangement of a body structure or function and is not synonymous with disability. (See 'Impairment' above.)
●Disability determination – Disability, the inability to engage in complex or gainful activity due to physical or mental impairment, is a result of the interaction between the impaired individual and the environment in which they function. Clinicians contribute to the determination of disability through their assessment of impairment, associated functional impairments, and any impact on the ability to perform activities of daily living and work. (See 'Disability' above.)
•For the purposes of the SSA, disability may be determined in several ways. Individuals who have "severe" impairment, as defined by disease-specific criteria in the Blue Book Listing of Impairments, are considered to be disabled and do not require a full evaluation process. "Medical equivalence" is recognized when multiple impairments result in functional limitations equal in severity to the requirements of a listing. Based on objective medical findings, other individuals may have sufficiently reduced "residual functional capacity" to qualify for disability. Proper documentation is essential to facilitate the disability process. (See 'Social Security Administration' above.)
●Assessment tools – While there are no tests with sufficient reliability, validity, or sensitivity to classify applicants as unable to work, tools can serve as useful adjuncts to the clinician's medical judgment (table 3). Condition-specific assessment tools are available to evaluate patients with functional limitations following low back pain, knee or hip replacement, or with nonspecific pain. The functional capacity evaluation, usually performed by a physical or occupational therapist, can provide information on job-specific maximum work ability. New advances in computer adaptive testing (CAT) are also available for use and can likely provide more accurate assessments about work capability. (See 'Disability assessment tools' above.)
●Worker's compensation – Worker's compensation is federally mandated, but criteria and administration are state-specific for most nonfederal jobs. (See 'Workers' compensation' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Meredith Kaplan, who contributed to earlier versions of this topic review.
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