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Am Fam Physician. 2008;77(12):1689

See related editorial on page 1655.

Author disclosure: Nothing to disclose.

Physicians are frequently involved in the assessment of impairment and disability as the treating physician, in consultation, or as an independent medical examiner. The key elements of this assessment include a comprehensive clinical evaluation and appropriate standardized testing to establish the diagnosis, characterize the severity of impairment, and communicate the patient's abilities, restrictions, and need for accommodation. In some cases, a functional capacity evaluation performed by a physical or occupational therapist or a neuropsychological evaluation performed by a neuropsychologist may be required to further clarify the functional capacity of the patient. The results of the impairment evaluation should be communicated in clear, simple terms to nonmedical professionals representing the benefits systems. These individuals make the final determination on the extent of disability and eligibility for benefits and compensation under that particular benefits system.

In the United States, roughly 49 million persons have physical or mental impairments that interfere with daily activities. An estimated 10.9 million persons, representing 6.6 percent of the working population, are unable to work. An additional 8.1 million persons are limited in the amount or type of work activity they can perform because of chronic health conditions.1

Clinical recommendationEvidence ratingReferences
Physicians should always determine their role in the evaluation, whether as a treating physician, new consultant, second opinion, or independent medical examiner.C3
When performing an impairment evaluation: establish the diagnosis, determine the severity of the condition, assess impairment impact, and assess functional ability.C5, 6
When writing the physician's report, use clear language and remember that it is intended for nonmedical personnel.C4


Impairment is defined as any marked loss or deviation in physiological function, psychological function, or anatomical structure of the body. An impairment may be temporary or permanent; progressive or static; intermittent or continuous; and may vary in severity or fluctuate over time.2 Impairment assessment is a medical evaluation; the physician's role is to determine the presence and severity of impairment and answer specific questions regarding appropriate treatment and prognosis related to the medical condition.

Disability is defined as the impact of impairment on a person's ability to meet the demands of his or her life.2 A disability may be temporary or permanent, and partial or total. Impairment does not necessarily imply disability. For example, a patient with newly diagnosed epilepsy who works as a commercial airline pilot will likely be permanently disabled from that occupation, whereas an office worker with newly diagnosed epilepsy may be able to perform his or her essential job functions without restriction, and therefore has no disability.

The Role of the Family Physician in Impairment and Disability Determination

Evaluation of impairment and disability is usually performed in the context of a person's job application, to determine benefits under an entitlement program, or for legal proceedings. When performing an impairment assessment, the physician should identify the third party making the request, delineate issues to be addressed, and determine his or her role (Table 1). It is important to clarify the role of the physician involved in the process, because a request for impairment assessment could be made of a treating physician, as a new consultation, or as an independent medical examination.3

Determine the third party making the requestEmployer, benefits administrator, insurer, attorney, judge
Determine nature of request and questionsDiagnoses, treatment, prognosis, impairment, causality, functional capacity, work capacity
Determine role as a physicianTreating physician, new consult or second opinion, independent medical examiner

If the physician has an existing relationship with the patient, he or she must obtain the consent of the patient to respond to these requests and release information to the third party (e.g., employer, benefits administrator, insurer, attorney, judge). The physician may bill the third party for the additional time required to generate the report. The treating physician's business office should decide on an appropriate hourly rate for this service and discuss it with any third party prior to completion.

A person also may be referred to the physician by a third party (usually the insurer) for an initial consultation, and possibly for an initiation of treatment to facilitate a return to work. In this situation, a doctor-patient relationship can be developed and follow-up is expected.

The person also may be referred for an independent medical examination. This type of evaluation is performed to furnish specific information to the third party pertaining to the health of the person. In this case, there is no doctor-patient relationship established and no follow-up is expected. The results of the evaluation are provided to the referral source, who also pays for the examination.4 There are potential advantages and disadvantages when a treating physician performs an impairment evaluation on an existing patient (Table 2). If the physician is not comfortable providing an opinion regarding the level of impairment, or believes that additional information may be helpful, the physician may advise the third party to refer the patient to another physician for further independent evaluation or testing.

Potential advantages
More objective and verified information about the patient's health status
More thorough understanding of the impact of the patient's impairment on function, based on numerous encounters
Impairment evaluation is a billable service to the third party requesting information
Potential disadvantages
Inadequate knowledge or skills to provide impairment evaluation or opinion
Negative impact on patient-physician relationship leading to concerns about trust and confidentiality
Symptom exaggeration by patient, which may adversely affect treatment
Difficulty in switching from the role of patient advocate to neutral examiner

Approach to Impairment Evaluation

The approach to impairment evaluation can be broken down into four steps (Table 3). The first step is to establish the medical diagnosis through history, physical examination, and appropriate diagnostic testing.5,6 The second step is to determine the severity of the condition.5,6 The examining physician is often asked to rely on “objective evidence”; however, in the reality of clinical medicine, many conditions are diagnosed solely on patient history. Thus, the physician should be able to classify the severity of the patient's condition based on a combination of complaints (subjective), physical findings (subjective and objective) and laboratory data (objective), where appropriate.

Establish medical diagnosis
History, physical examination, diagnostic studies
Determine severity of the condition
Asymptomatic, mild, moderate, severe, end-stage disease
Assess impairment
Impact of disease on organ function (measured as loss of function)
Assess impact on functional ability
Ability to perform work, leisure, self-care, and social activities

The third step is to assess the impact of impairment on affected organ systems, which is measured as loss of function. To aid in this assessment, organizations such as the Department of Veterans Affairs,7 the American Medical Association,5 the Social Security Administration8 and state workers' compensation boards have developed their own detailed guidelines for the evaluation and uniform classification of disease severity (Table 479 ). When evaluating impairment of patients under a specific benefits system, the physician must use the appropriate guidelines.

The fourth step is to determine the impact of impairment on functional ability.5,6 If the purpose of the evaluation is to determine whether the patient can perform a specific job, then the objective is to predict the level at which the patient can safely and dependably perform the essential functions of that job. This requires a detailed knowledge of the tasks involved in the job.

Department of Veterans Affairs
Electronic Code of Federal Regulations (e-CFR). Title 38: Pensions, Bonuses, and Veterans' Relief: Chapter 1. Department of Veterans Affairs. Part 4. Schedule for Rating Disabilities7
Social Security Administration
Disability Evaluation Under Social Security8‎
Occupational Therapy Association
Consumer Fact Sheets. Functional Capacity Evaluation9

Specific Types of Evaluation


A prediction of function often can be made based on the clinical assessment described above. If the physician has difficulty predicting function, particularly related to work recommendations, a more formal assessment via a Functional Capacity Evaluation (FCE) may be desired. An FCE includes a standardized battery of functional measures performed by physical or occupational therapists using performance-based testing and are designed to predict a person's ability to perform work-related activities.10 The measures are especially useful for patients with muscu-loskeletal problems.

There are two basic types of FCEs. The first type is a general evaluation that is used when a patient has no specific job to which to return. This type of FCE assesses the patient's abilities to perform various generic tasks related to the physical demands of work, the performance of which can be used for vocational planning. The second type of FCE is a job-specific evaluation, which is used to help determine if the patient is ready to return to specific job demands. Therefore, the reason for obtaining an FCE should be clearly stated in the referral.

No standard protocol for an FCE exists; rather, the evaluation may include a wide range of tests and activities. Typically, FCEs are performed by physical or occupational therapists and are designed to test several physical parameters: strength and endurance; positional or postural tolerance; coordination; body mechanics; the ability to perform repeated activities; and work-simulation activities (if indicated). Specific work simulation activities can be structured based on the reasons for obtaining the FCE. Depending on its format, the FCE testing period may range from four to six hours and may take place over two consecutive days.9,11 Indications and contraindications for an FCE referral are shown in Table 5.11

Maximal medical improvement achieved, but questions remain regarding return to work capability
Quantification of physical capabilities for disability determination
Quantification of functional abilities prior to vocational planning or return to work
Quantification of functional abilities to assist with vocational planning or medicolegal settlement
Medically unstable patient
Presence of medical problems that may be impacted by testing (e.g., cardiopulmonary problems)
Inability to communicate with evaluator to understand directions or voice concerns

Recommendations regarding whether the patient can safely perform a combination of specific and general tasks are made by the evaluator, based on the patient's FCE results. These recommendations help the physician determine if it is feasible for the patient to return to his or her full duties or modified duties.12

Although the results of an FCE provide recommendations regarding a person's functional capabilities, a successful return to work depends on more than functional capacity alone. Performance on an FCE and a successful return to work may be influenced by physical and psychosocial factors, including self-perception of disability, pain intensity, pain-related fear, illness behavior, and self-efficacy.12,13 Therefore, screening for psychosocial factors that may influence functional performance may be a useful adjunct to FCE and can be measured via instruments such as the Pain Disability Index14,15 or a simple visual analogue scale.16 The role that psychosocial job factors (e.g., job stress, secondary gain) may play in results of an FCE remains unclear.13


Many patients are referred for impairment evaluations related to mental health diseases, which often complicate other medical conditions. Psychiatrists or psychologists are the preferred examiners for assessing mental health impairment.

Much of the evidence in the evaluation of mental health impairment is subjective or based on the unverified self-report of the patient. Establishing the presence of impairment in this situation may be more difficult because the unsupported subjective report of even an apparently honest claimant may not be considered sufficiently reliable evidence in a medicolegal context. It may also be more difficult to identify exaggeration or fabrication of symptoms. Therefore, the examiner must acknowledge these challenges of subjectivity and ambiguity, and compensate to the degree possible. The reliability of an evaluation for mental health impairment may be improved by focusing on several factors, including an assessment of the patient's motivation to return to work,17 and whether there is evidence of deception18 (Table 6).

Gather detailed and specific information about diagnoses, symptoms, signs, and impairments of illness
Use multiple, objective, and verifiable sources of information about the patient's functioning
Pay attention to any inconsistencies observed or reported in the presentation, diagnosis, treatment, and course of the patient's condition


Patients who complain of cognitive deficits, especially with normal or minimally impaired mental status examinations, are candidates for neuropsychological assessment. This evaluation, usually performed by a neuropsychologist, involves the systematic study of behavior using standardized tests that provide relatively sensitive indices of brain-behavior relationship covering a range of cognitive domains. Information from neuropsychological assessment can define the patient's functional limitations and residual cognitive strengths.19 A thorough neuropsychological evaluation should also contain one or more tests with validity scales to assess inadequate effort or exaggeration of cognitive deficits.20


Disability assessment has a broader focus than impairment assessment because factors such as essential requirements of a job, reasonable accommodation, educational level of the patient, transferable skills, and potential for retraining have to be considered. Disability can also be assessed in terms of the impact of impairment on activities of daily living (e.g., self-care, mobility) without reference to a specific occupation.

Information on impairment that is provided by the physician is used by administrators to determine the extent of disability and is translated into benefits, including finan-cial reimbursements.21 The process by which disability is assigned varies according to the criteria for eligibility and entitlement under specific programs (Table 479 ). Examples of entitlement programs include the Department of Veterans Affairs compensation and pension program, Social Security insurance, state workers' compensation programs, and private disability insurance.

Physician's Report

The information generated for a disability evaluation is often used by nonmedical professionals. Therefore, the report should be written for that audience. Initial information and physical capacities forms are typically obtained from medical records of treating physicians. Certain limitations can be determined based on the underlying medical condition. For instance, a patient with newly diagnosed asthma should be restricted from exposure to any respiratory irritant, including smoke, dust, fumes, and temperature extremes. Likewise, a patient with carpal tunnel syndrome may require restrictions from repetitive or continuous upper-extremity activity. Other functional limitations involving the musculoskeletal system (e.g., tolerance for sitting, standing, walking) may be determined based on the physician's experience with such cases. If the patient has undergone physical therapy for his or her condition (e.g., lumbar strain or sprain), the treating physical therapist can provide additional clarification regarding the patient's functional tolerances. Treating physicians may generate a summary report explaining the basis for any restrictions identified. Physicians may bill the third party for the additional time required to generate summary reports. Sample physician report templates covering impairment assessment are available for reference.5,22

Independent medical examinations and consultations require a comprehensive report that should include a summary of reviewed medical records, the detailed medical assessment performed, a summary of questions being addressed, and the degree of impairment from the identified condition that references the impairment scheme used.

Certain benefit systems also inquire about causality and attribution. Causation determines whether a specific exposure or injury was the cause of or a significant contributory factor to the impairment. Causality in impairment and disability evaluation is determined using the legal standard of “more probable than not” or a greater than 50-percent probability.21 This requires understanding the causes of the specific disease or disorder leading to the impairment, identifying the presence of one or more causative factors given the specific situation, and understanding the natural history of the disease as it relates to exposure to the suspected agents. Multiple factors may increase the risk of a disease; therefore, knowledge of the interactive effects of these factors is important. Establishing a temporal relationship between a specific exposure and the onset of the disease is also important (e.g., an exposure to asbestos with the development of lung cancer). Other factors, including appropriate latency (i.e., the period between initial exposure to an agent and the development of the disease), are also important in determining causality.

Finally, some systems can request the examining physician to determine the contribution of several diseases to the final impairment (e.g., a patient who is diagnosed with chronic obstructive pulmonary disease and asbestosis) or multiple causes or risk factors in the etiology of a disease (e.g., occupational exposure to polycyclic aromatic hydrocarbon, a known carcinogen, in a smoker who is diagnosed with lung cancer). This is called apportionment, and these determinations rely on the judgment of the examining physician using available literature to support the conclusions.

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