Common Measures of Disability

Function

When evaluating and determining disability, healthcare professionals must document specific clinical signs or laboratory results in accordance with the requirements of the relevant agency. Key details include findings related to the medical conditions or impairments and their severity, functional limitations, and associated restrictions. Agencies requesting this information may include the Social Security Administration, Workers' Compensation programs, and private organizations. Many states adopt portions of the American Medical Association's Guides to the Evaluation of Permanent Impairment as a standardized framework. Additionally, clinicians are responsible for documenting any changes in the patient's condition. In the United States, an impairment is considered permanent or at maximum medical improvement if no significant change is expected or observed over the course of 12 months. 

Models of Disability

The conceptualization of disability has evolved, yet variations across statistical systems persist due to differences in concepts and methodologies. Traditional censuses face challenges in accurately quantifying disabilities within a population, as they often use universal questions that fail to capture all disabling conditions or their effects on autonomy and equality. Researchers typically rely on 2 primary models for common measures of disability—the medical and social models—with the ICF emerging more recently. The clear distinction between the medical and social models is essential in shaping the definition and measurement of disability.[13][14]

Medical model: The medical model views disability as an individual issue, which stems from bodily or mental impairment that requires either cure or compensation, often overlooking broader social factors that contribute to disability.[15][16] This model frames disability as a personal tragedy and a biomedical problem, emphasizing the need to fix the individual rather than addressing social exclusion and disadvantage.[17]

Social model: The social model, in contrast, views disability as a mismatch between individual capabilities and environmental demands, which are driven by societal organization and attitudes.[17] This model emphasizes that society constructs disability and can address it through changes in policies, practices, and ways of thinking.[18] The social model emerged from advocacy and civil rights movements. This model emphasizes that disability arises from social inaccessibility rather than individual deficits. This model carries significant implications for institutions and policies, focusing on environmental and social changes to ensure equal participation for individuals with impairments.[19][20][21][22]

Biopsychosocial model: The ICF, a biopsychosocial model introduced by the WHO, provides a framework for identifying and describing disability in terms of body functionality and structure, activities and participation, environment, and personal factors. The main objectives of this model include:

• Providing a scientific base for identifying and studying health-related states, consequences, and determinants, as well as establishing common knowledge for describing health and health-related states.
• Facilitating improved communication among healthcare professionals, researchers, policymakers, the public, and people with disabilities.
• Enabling comparison of health data across countries, healthcare disciplines, and services. 
• Offering a systematic coding scheme for health information systems.[23][24]

The ICF consists of 2 main parts, each with 2 additional subcategories, as mentioned below.

• Part 1 of the ICF provides a framework for discussing a person's functioning and disability. This part has 2 components—body functions and structures, as well as activities and participation. Body functions and structures describe anatomy, physiology, and changes in anatomical structures or physiological systems. Activities and participation describe a person's functional status in areas such as communication, mobility, self-care, and learning.
• Part 2 of the ICF focuses on contextual factors that consider environmental and personal influences affecting a person's functional ability.[23][24][25] 

Commonly Used Disability Scales

Determining disability status is a complex process, with the appropriate methodology depending on the population, setting, and available resources. Widely used methods for assessing disability include:

• A self-identification question asking whether the person has a disability.
• An impairment-based question inquiring about loss of vision, hearing, physical mobility, or other physical, mental, or emotional difficulties.
• Functional questions addressing issues with specific symptoms or activities.[26][27]

Researchers often use multiple methods to assess the presence of a disability. Clinicians rely on well-established disability scales, which offer more detailed insights into the types and extent of limitations experienced by individuals with mobility impairments compared to isolated patient interviews.[28]

Patient-Reported Outcomes Measurement Information System

The Patient-Reported Outcomes Measurement Information System (PROMIS), developed by the National Institutes of Health, evaluates health and function through self-reported assessments across more than 300 physical, mental, and social health measures. These measures focus on 5 key domains—physical function, pain, fatigue, emotional distress, and social support. A widely used measure is the Pain Disability Index. PROMIS assessments are available in both print and digital formats. Additional information and access to these measures can be found on the PROMIS Measures website: https://www.healthmeasures.net/explore-measurement-systems/promis/obtain-administer-measures.

Expanded Disability Status Scale 

The Expanded Disability Status Scale is a method for quantifying and monitoring disability progression in individuals with multiple sclerosis by assessing 8 functional systems—pyramidal, cerebellar, brainstem, sensory, bowel and bladder, visual, cerebral, and other functions. The Expanded Disability Status Scale scoring ranges from 0 to 10 in 0.5-unit increments, based on neurological examination findings, with higher scores indicating significant disability.[29]

Guy's Neurological Disability Scale

Guy's Neurological Disability Scale is a comprehensive tool used to assess the degree of disability or dependence in daily activities among individuals with neurological conditions such as multiple sclerosis or stroke. This scale evaluates 12 aspects of an individual's functional abilities, including mobility, hand function, vision, speech, cognition, and mood. Clinicians score each of the 12 items individually, ranging from 0 (indicating no disability) to 5 (indicating maximum disability). The total score is the sum of these individual scores, with a possible range from 0 to 60. A higher total score indicates a greater level of disability.[30]

Barthel Index of Activities of Daily Living 

The Barthel Index of Activities of Daily Living is a tool used to assess an individual's ability to perform basic activities of daily living independently, such as feeding, bathing, grooming, dressing, bowel control, bladder control, toilet use, transfers, mobility, and stair climbing. This index is particularly useful for evaluating the functional status of patients with chronic illnesses, neurological conditions, or those recovering from surgery. Healthcare professionals score each activity based on the level of assistance the person requires. Individual scores typically range from 0 to 15, with a maximum possible total score of 100. Higher scores indicate greater independence, while lower scores reflect a higher degree of dependency.[31]

The Ashworth Scale of Spasticity 

The Ashworth Scale of Spasticity measures the resistance encountered during passive muscle stretching, serving as an indicator of spasticity. The original scale uses a 0 to 4 scoring range, where 0 indicates no increase in muscle tone and 4 signifies rigidity in either flexion or extension. The current version of the scale allows for a more nuanced assessment, maintaining the 0 to 4 range but including an additional score of 1+ between 1 and 2.[32]

Activities of Daily Living Scales 

The activities of daily living scales consist of a set of 2 evaluations utilized in healthcare to assess an individual's ability to perform essential daily tasks independently.[33] The activities of daily living are classified into "basic" and "instrumental," as mentioned below.

• Basic activities of daily living include tasks necessary for managing one's fundamental physical needs, such as personal hygiene, grooming, dressing, toileting, transferring or ambulating, and eating.
• The Instrumental Activities of Daily Living Scale evaluates a person's ability to perform more complex tasks that are important for independent living but not essential for basic self-care. Some items assessed in the Instrumental Activities of Daily Living Scale include managing finances, meal preparation, housekeeping, using transportation, managing medications, and handling phone communication. The Instrumental Activities of Daily Living Scale now also includes activities such as leisure, attending church, and engaging in paid or volunteer work, all of which are essential for independent community living.[23] Assessing activities of daily living provides valuable insight into an individual's level of self-sufficiency and the amount of assistance they may need. These scales are widely used in care settings for older adults, individuals with disabilities, and those recovering from injuries.[33][34][35]

The World Health Organization–Disabilities Assessment Scale 2.0

The WHO Disabilities Assessment Scale 2.0 is a comprehensive, generic scale designed to measure disability across a wide range of health conditions. The scale serves as a cross-cultural tool that captures social, occupational, physical, and role impairments associated with a health condition. This scale assesses functioning and disability independently of the underlying pathology, covering 6 domains, including cognition, mobility, self-care, getting along, life activities, and participation, which are associated with 36 items. The scale reflects the biopsychosocial model as outlined in the ICF and is also available in a shorter version containing 12 items.[36]

Rather than limiting the models for common measures of disability to just medical and social categories, some authors categorize them into 7 groups—functional limitations, activity limitations, participation restrictions, self-report measures, medical assessments, assistive technology use, and environmental assessments.

Self-Report Measures

Self-report measures are tools used to collect information directly from individuals about their experiences, symptoms, behaviors, or perceptions related to their health or well-being. These measures rely on individuals' self-assessments to report specific aspects of their condition or functioning, providing valuable insights into how they perceive and experience various health-related factors. Numerous condition-specific questionnaires exist. For example, healthcare professionals often use up to 10 different low back pain questionnaires to assess functional limitations associated with the condition. The Oswestry Disability Questionnaire, for instance, evaluates pain and complex activities. Please see StatPearls' companion resource, "Seating And Wheelchair Evaluation," for more information.

The Short Form 36 Physical Functioning Scale evaluates a patient's perceptions regarding their general health in addition to their physical, social, and emotional functioning.[38] Clinicians who frequently treat specific conditions should consider using validated questionnaires as part of routine care. Common orthopedic measures include the Disability of the Shoulder, Arm, and Hand (DASH) Questionnaire, the American Academy of Orthopedic Surgeons Lower Limb Questionnaire, and the Lower-Limb Tasks Questionnaire.[39]

Pain assessment tools or questionnaires and self-report measures have a key role in evaluating the impact of various health conditions on a patient's function and well-being. Commonly used tools include:

• The McGill Pain Questionnaire and the Pain Disability Index, which are designed to assess pain intensity and its impact on daily functioning.
• The Patient Health Questionnaire-9 and Generalized Anxiety Disorders Assessment, which assess self-reported symptoms and functional impairments in individuals with depression or anxiety. Please see StatPearls' companion resource, "Disability Evaluation," for more information.[41]
• The Quality of Life Inventory, which rates perceived quality of life across different domains for individuals with multiple sclerosis and HIV or AIDS.[42]

Functional Limitations

Functional capacity examinations, often conducted by physical or occupational therapists, objectively assess an individual's work abilities. Instead of a physical capacity examination, the Roland Morris Disability Questionnaire may be used to measure functional status. Additionally, clinicians commonly use the following tools to evaluate the impact of various health conditions on an individual's physical functioning, independence, and activities of daily living.

• The Activities of Daily Living Index measures a person's ability to perform basic tasks such as eating, bathing, and dressing.
• The Modified Rankin Scale assesses the functional ability of individuals with stroke and other neurological conditions to perform activities of daily living.[43][44]
• The Functional Independence Measure (FIM) evaluates the level of independence in activities such as walking, bathing, and toileting for individuals with a spinal cord injury or traumatic brain injury.[45]

The FIM is an 18-item tool, comprising 13 motor and 5 cognitive tasks, that provides a comprehensive assessment of self-care, mobility, communication, and cognitive abilities.[29] A similar measure, the Barthel Index, is a 10-item tool that focuses primarily on basic activities of daily living, such as bathing, dressing, and eating. Clinicians use both measures in rehabilitation settings; however, the FIM uses a more detailed scoring system with multiple levels of assistance, which evaluates a patient's ability to perform daily activities independently across domains such as self-care, sphincter control, transfers, locomotion, communication, and social cognition.

Each task on the FIM is rated on a 7-point scale, with 1 indicating total assistance and 7 signifying complete independence. The total score ranges from 18 (indicating entire dependence) to 126 (indicating total independence), thereby allowing clinicians to monitor changes in a patient's functional status throughout rehabilitation.

The Barthel Index scoring is as follows:

• 0 = Unable
• 1 = Needs assistance or help
• 2 = Independent

Clinicians calculate the total score and multiply it by 5, with a maximum possible score of 100. A score of 0 to 20 indicates total dependency, 21 to 60 severe dependency, 61 to 90 moderate dependency, and 91 to 99 slight dependency.[30] Both measures are useful for tracking progress during rehabilitation. 

Activity Limitations 

Activity limitations refer to challenges or restrictions an individual may encounter when performing specific tasks or actions. These difficulties can arise from health conditions, disabilities, or injuries, and can potentially affect a person's ability to perform daily activities or engage in various forms of participation.

• The Short Physical Performance Battery assesses physical function and mobility limitations in individuals with osteoarthritis and peripheral neuropathy.[31]
• The Brief Pain Inventory estimates the impact of pain on daily activities and functioning in individuals with fibromyalgia and cancer.[32]

Participation Restrictions 

Participation restrictions refer to limitations or barriers that hinder an individual's involvement in social, recreational, vocational, or community activities. These restrictions are often associated with health conditions, disabilities, or environmental factors that obstruct or prevent full participation in various aspects of life.

• The Community Integration Questionnaire measures social participation and community integration for individuals with acquired brain injury and schizophrenia.[33]
• The Work Limitations Questionnaire assesses the impact of health conditions on work-related activities for individuals with chronic low back pain and arthritis.[34]

Medical Assessments 

Medical assessments evaluate an individual's health status, medical history, symptoms, and physical condition to diagnose health conditions, monitor disease progression, and determine appropriate treatment plans. These assessments are conducted by healthcare professionals, such as physicians or advanced practice practitioners, to gather vital information about an individual's health and formulate an accurate diagnosis and management plan. 

• The Mini-Mental State Examination assesses cognitive function and screens for dementia in individuals with Alzheimer disease and mild cognitive impairment.[35]
• Spirometry measures lung function and evaluates respiratory disability in individuals with asthma and chronic obstructive pulmonary disease.[36]

Assistive Technology Use

Assistive technology refers to tools, devices, equipment, or systems designed to help individuals with disabilities or limitations perform tasks, improve functional abilities, and enhance overall independence and quality of life. Assistive technology can range from simple, low-tech devices such as grab bars and adaptive utensils to high-tech solutions such as communication devices, powered wheelchairs, and computer software with accessibility features.

• The Wheelchair Seating and Positioning Assessment determines the most appropriate wheelchair and seating system for individuals with spinal cord injuries and cerebral palsy. Please see StatPearls' companion resource, "Seating And Wheelchair Evaluation," for more information.
• The Communication Aid Assessment identifies and customizes communication devices to enhance interaction and expression for individuals with amyotrophic lateral sclerosis and cerebral palsy.[37]

Environmental Assessments 

Environmental assessments evaluate the impact of physical, social, economic, and other environmental factors on individuals or communities. These assessments aim to identify potential hazards, risks, challenges, or opportunities in the environment that may affect the health, well-being, or quality of life of individuals. 

• The Accessibility Audit assesses barriers in the built environment, such as ramps, doorways, and bathroom facilities, for individuals with physical disabilities and wheelchair users.[38]
• The Social Support Network Assessment evaluates the availability of social support and community resources that facilitate participation in various activities for individuals with chronic illnesses and mental health conditions.[39]

Issues of Concern

Determining disability is a complex and multidimensional process. The assessment and definition of disability are challenging due to the diverse criteria, models, and personal and societal factors that influence how disability is understood and measured. Using standard measures of disability can be challenging because organizations, institutions, and countries often have different criteria for defining disability. These definitions may vary significantly regarding the conditions considered, the severity required for a condition to be classified as a disability, and the methods used for assessment. For example, in the United States, a disability is defined as a physical or mental impairment that substantially limits one or more major life activities. Please see StatPearls' companion resource, "Disability Evaluation," for more information.

At the same time, the Equality Act in the United Kingdom defines disability as a physical or mental impairment that has a "substantial" and "long-term" negative effect on a person's ability to carry out normal daily activities. International standards also vary. The WHO adopts a broader approach through the ICF, defining disability as an umbrella term encompassing impairments, activity limitations, and participation restrictions. The ICF highlights the interaction between health conditions and contextual factors.

In contrast, the National Institutes of Health (NIH) uses specific criteria that vary depending on the research context and health outcomes studied. This variation makes comparing data challenging, complicates policy development and resource allocation, and hinders researchers' ability to conduct meta-analyses and systematic reviews—key methods for understanding the global burden of disability and evaluating interventions.[40][41] Moreover, disabilities can change over time due to medical, technological, or personal developments. Common measures may not capture these changes effectively and may require frequent updates to remain relevant.

Balancing the medical and social models of disability presents unique opportunities and challenges, each providing valuable perspectives. However, disability measures often fail to fully capture the complex interplay between individual impairments, societal barriers, and contextual factors. The medical model focuses on individual impairments and health conditions, emphasizing medical interventions to improve functioning and determining eligibility for benefits based on diagnoses. While this approach is important, it can lead to stigmatization, overlook the social and systemic factors influencing disability, and fail to account for personal experiences and autonomy.

The social model of disability highlights the societal barriers and discrimination that contribute to disability, advocating for inclusion, accessibility, and environmental adaptations. This model empowers individuals with disabilities to challenge exclusionary norms and advocate for their rights. However, critics argue that it may downplay the significance of individual impairments and the need for medical interventions. Additionally, implementing systemic changes can be complex and time-consuming, and some individuals may find it difficult to fully embrace the model due to personal experiences with lifelong impairments. To provide a comprehensive evaluation, clinicians must recognize the nuances of both models and adopt a more holistic approach that integrates and balances medical and social perspectives in understanding and addressing disability.

The reliance on self-reported measures of disability introduces significant variability, as individual perceptions, cultural influences, and environmental factors shape how disabilities are experienced and reported. Common disability measures based on self-reporting are inherently subjective, as individuals with similar conditions may perceive and report their symptoms differently. These differences can be influenced by cultural factors, personal expectations, past experiences, and their knowledge of the condition.[42] Environmental and social factors, such as accessibility, social support, and societal attitudes, can significantly influence disabilities. However, standard measures often fail to account for these contextual variables.[43] Clinicians must recognize that disability measures can have a profound impact on the development and implementation of policies and services. Inaccurate or incomplete measures may result in inadequate support and resources for individuals with disabilities.[44]

Clinical Significance

Standardized disability measures are crucial in clinical practice as they provide a comprehensive framework for assessing and managing disabilities. These tools, ideally incorporating models such as the ICF, enable healthcare professionals to account for physical, environmental, and personal factors affecting a patient’s functioning and quality of life. This approach supports accurate diagnoses, effective treatment planning, and targeted interventions that address both the medical and social dimensions of disability. Such measures guide personalized care, help monitor progress, and assess intervention effectiveness. They allow clinicians to understand patients’ limitations, design tailored rehabilitation programs, and recommend appropriate assistive technologies or modifications, ultimately improving patient outcomes, satisfaction, and quality of life.

Additionally, measuring disability is essential for estimating prevalence, identifying needs, and monitoring inclusion. Precise measurement enables the quantification of service requirements, analysis of disability life courses, and development of targeted prevention strategies. It also ensures fair comparisons across populations, identifies disparities, and tracks changes over time, avoiding misattributions of cause and effect.

Enhancing Healthcare Team Outcomes

Disability refers to the inability to engage in a major life activity due to an impairment. Assessing disability requires a multifaceted approach that incorporates both clinical and nonclinical information. When conducting a disability evaluation, healthcare professionals must consider the individual's medical condition, functional abilities, and environmental factors, such as the workplace environment and knowledge of the patient's job. Prevalence estimates of disability vary widely, reflecting differences in definitions, screening tools, and study methodologies. This variability underscores the complexity and context-dependent nature of disability.

An accurate and comprehensive evaluation, supported by information from all treating clinicians and allied healthcare professionals, is essential, as disability status has a significant impact on a patient's well-being. Disability status individually affects factors such as earnings, ability to return to work, work productivity, and access to current and future healthcare needs. The disability evaluation process relies on medical assessments, functional capacity evaluations, and validated questionnaires, ideally within the framework of a disability assessment model such as the ICF developed by the WHO. The ICF offers a standardized and comprehensive approach to understanding disability by integrating health, personal, and environmental factors, although resource constraints often limit its full implementation.

Disability measures are crucial for diagnosing, monitoring, and personalizing interventions to address individual needs, fostering patient-centered care. Additionally, they are crucial in public health planning and guiding social and economic decision-making. Socially, these measures help combat stigma, direct resource allocation, and improve the quality of life for individuals with disabilities by promoting support systems, educating the broader community, and fostering inclusive environments. Economically, standardized measures provide valuable insights into healthcare costs and resource management, enabling policymakers to design laws and programs that align with international standards.

The interprofessional healthcare team plays a vital role in delivering comprehensive, patient-centered care. By fostering collaboration among physicians, advanced practice providers, nurses, therapists, social workers, and mental health specialists, the team ensures a holistic approach to assessing and managing disabilities. In addition to documenting the patient's clinical findings, impairment severity, and functional limitations, clinicians must integrate input from all healthcare team members to form a comprehensive picture of the patient's condition. Each healthcare team member brings specialized expertise to patient care. Physicians and advanced practice professionals focus on diagnosing conditions and recommending appropriate treatments, whereas social workers identify environmental and social barriers and assist patients in accessing essential resources.

Nurses are crucial in fostering communication among healthcare team members, administering disability measures, and providing patient education. Physical and occupational therapists play a vital role in evaluating functional limitations, supporting rehabilitation, and providing guidance on home and workplace accommodations to improve quality of life. Effective communication, including regular meetings, shared health records, and collaborative care models, is essential for coordinating efforts and making informed care adjustments. This teamwork fosters a responsive and inclusive approach by enhancing medical management, functional outcomes, and the overall quality of life for individuals with disabilities. By promoting collaboration and valuing the essential contributions of all professionals, healthcare teams can reduce disparities, ensure equitable care, and achieve better patient outcomes.

Nursing, Allied Health, and Interprofessional Team Interventions

Nursing interventions are crucial for assessing and managing disabilities in patients, as well as addressing their physical and psychosocial aspects. Nurses use standardized disability measures to evaluate patients, manage symptoms, and coordinate care. They also educate patients and families on the use of assistive devices, medication adherence, and lifestyle modifications. Additionally, nurses advocate for reducing stigma and enhancing the overall quality of life for individuals with disabilities.

Allied healthcare professionals, including physical and occupational therapists, speech and language pathologists, and social workers, contribute specialized expertise to disability management. Physical and occupational therapists utilize disability measures to improve mobility and daily living skills, whereas speech and language pathologists focus on addressing communication and swallowing difficulties. Social workers support patients by navigating healthcare systems, connecting them to resources, and helping manage emotional challenges.

Interprofessional healthcare team interventions provide holistic, patient-centered care through collaboration across various healthcare disciplines. The healthcare team comprehensively addresses physical, mental, and social needs by sharing care plans, holding regular team meetings, and maintaining effective communication. This collaborative approach improves patient outcomes, fosters inclusivity, and highlights the importance of each team member's contributions, aligning with principles of teamwork and equality in healthcare.

Nursing, Allied Health, and Interprofessional Team Monitoring

Nursing monitoring is crucial in assessing and treating patients with disabilities. Nurses closely observe changes in patient conditions, detect early signs of complications, and evaluate the effectiveness of care plans using measures of disability. Nurses can identify changes in the patient's condition and implement timely interventions or care adjustments by maintaining detailed records and conducting regular check-ins.

Allied healthcare professionals contribute to specific aspects of recovery and rehabilitation. Physical therapists monitor mobility progress, occupational therapists evaluate daily living skills, and speech and language pathologists assess communication and swallowing abilities. These healthcare professionals adapt therapies to effectively meet patient goals and support recovery.

Interprofessional team monitoring emphasizes collaboration among healthcare professionals to ensure comprehensive care. Regular interdisciplinary meetings and shared health records enable timely updates, care plan adjustments, and a holistic understanding of patient needs. This team-based approach enhances patient safety, satisfaction, and outcomes by addressing the evolving needs of individuals with disabilities.