Chapter 6 Impairment Rating and Disability Determination

This chapter includes a brief introduction to the latest (sixth) edition to the American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment,⁴⁸ a reference text that can be likened to an updated tax code for impairment rating. The sixth edition chief editor is Robert D. Rondinelli, a physiatrist. In contrast to previous editions of the AMA Guides, it is fortunate that the sixth edition moves toward a more functional view of impairment rating.

This chapter provides basic information about disability and impairment evaluations. It covers four main topics:

1. The types of agencies that administer impairment and disability programs

2. The concepts central to this area of medicine

3. The physician’s role in performing these evaluations

4. Practical strategies for disability evaluation

While physicians of many different specialties are actively involved in disability and impairment evaluation, physiatrists have skills that are central to understanding disability and impairment evaluation. The physiatric emphasis on assessing and restoring function among the severely ill or injured provides a key component of what is typically needed by agencies requesting disability evaluations.

This chapter is not intended to be used to determine impairment or disability for a specific patient. The reader is referred in this regard to the AMA Guides,⁴⁸ which outlines a method for rating impairment for virtually every organ system. In practical terms, however, most impairment and disability evaluations focus on musculoskeletal disorders.

Disability Agencies

During the past 100 years, the informal assistance within communities to help those with disabilities has been supplemented or replaced by formal disability programs. To receive benefits, an individual having a medical problem must submit an application to an agency that administers a disability program. Adjudicators from the agency then determine whether the applicant meets the eligibility criteria for benefits. To make this determination, the adjudicators typically request medical information from the applicant’s treating physicians. Physiatrists in particular are drawn into the disability determination process because they often treat patients with severe neurologic and/or musculoskeletal conditions. Disability and impairment systems include the Social Security Administration (SSA), workers’ compensation, the Veterans Administration (VA), and private disability insurance programs.

Impairment and disability are not absolutely defined and rated within a single system but are dependent on particular administrative systems. For example, workers’ compensation systems in the United States are no-fault insurance programs that are regulated at the state level and vary considerably from one state to another. Coverage is available for workers who have documented occupational injuries or “occupational exposures” (such as cumulative trauma disorders). Benefits can include medical care, time-loss benefit payments, vocational retraining if needed, and payment for impairment at the time of claim closure.

Assessment of impairment or disability must be done within the guidelines of an individual system. The term disability agency is used in this chapter to refer to any organization that evaluates disability applications or dispenses disability benefits.

Private disability agencies might award claimants who are no longer able to perform within their profession, but they might require that the claimant be unemployable in other professions as well. There is often a requirement of continuous disability of at least 6 months, and there can be an additional requirement that the claimant apply for and be eligible for Social Security Disability.

The SSA has its own set of guidelines for determining disability. If claimants are found eligible, they are awarded disability payments on an ongoing basis, as well as eligibility for Medicare or Medicaid. For claimants to be considered eligible for Social Security, they must be totally disabled from any gainful employment, and they must have an impairment that is considered “disabling” and likely to last or have lasted at least 12 months.

The VA has its own disability benefits program, described as follows:

Disability compensation is a monetary benefit paid to veterans who are disabled by an injury or disease that was incurred or aggravated during active military service. These disabilities are considered to be service-connected. Disability compensation varies with the degree of disability and the number of veteran’s dependents, and is paid monthly.⁶⁰

Definitions: Disability and Impairment

Social Security Administration

Agencies have different definitions of disability. For example, the SSA defines disability as “the inability to engage in any substantial gainful activity … by reason of any medically determinable physical or mental impairment that can be expected to result in death or that has lasted or can be expected to last for a continuous period of not less than 12 months.”⁵⁶ To determine work disability, the SSA uses a sequential evaluation process that focuses on applicants’ diagnoses, not their functional abilities. Although the SSA’s five-step process assesses earnings and impairment severity, it is not until late in the process that functional capacity is assessed. An applicant may appeal an unfavorable disability determination, which can markedly extend processing time. Unlike the VA, the SSA does not award benefits for “partial disability.”

The SSA disability programs influence the lives of millions of adults and children. As growing numbers of applicants apply for benefits, the agency is being pressured to meet very high demands. To improve the SSA’s determination process, an increased consideration of functional ability is likely needed.

AMA Guides, Sixth Edition

The latest edition of the AMA Guides ⁴⁸ uses as its foundation the World Health Organization model of disablement. This model is called the International Classification of Functioning, Disability, and Health (ICF) and is illustrated in Figure 6-1. There are three key inputs to the ICF model determining disability, paraphrased here from the AMA Guides⁴⁸:

1. Body functions and body structures: These can vary from the normal state, and these losses are called impairments.

2. Activity: Task execution by the individual. Activity limitations are difficulties with carrying out such activities.

3. Participation: Involvement in life situations. Participation restrictions are barriers from such involvement.

Note that body functions are physiologic—for example, the ability of the upper limb to generate accurate motion and strength. Body structures are anatomic—for example, the upper limb itself. Either or both can be compromised to produce impairment. The inability to carry out tasks, such as not being able to comb one’s hair, is an activity limitation. The inability to be involved in a typical life situation, such as being gainfully employed and interacting with one’s peers, is a participation restriction. Note that there is not a necessary correlation between activity limitation and participation restriction.

FIGURE 6-1 The World Health Organization ICF Model of Disablement.

(Redrawn from Rondinelli RD, editor: Guides to the evaluation of permanent impairment, ed 6, Chicago, 2008, American Medical Association Press.)

In the ICF model, there is no linear progression from pathology to impairment to disability and to participation restriction. The AMA Guides justifies the use of the ICF model as follows ⁴⁸:

The ICF model appears to be the best model for the Guides. It acknowledges the complex and dynamic interactions between an individual with a given health condition, the environment, and personal factors. The relationships between impairment, activity limitations, and participation are not assumed to be linear or unidirectional. An individual may experience measurable impairment without significant activity limitations that do not produce restrictions to major life activities such as work or recreation. On the other hand, one can experience significant activity limitations and/or participation restrictions in the absence of demonstrable impairment.

The reader should note that this framework for distinguishing impairment from disability is natural for the physiatrist. As medical professionals, physiatrists have core training in diagnosing and treating loss of body function and structure, but they also ask about the ability of patients to control their environment. Specifically, physiatrists focus on mobility deficits, including ambulation and transfers, and on activities of daily living (ADLs), including instrumental ADLs. Using the ICF framework, the AMA Guides defines impairment and disability as follows:

Impairment: A significant deviation, loss, or loss of use of any body structure or body function in an individual with a health condition, disorder, or disease.

Disability: Activity limitations and/or participation restrictions in an individual with a health condition, disorder, or disease.

Impairment rating within the latest AMA Guides ¹⁰ has more weight given to loss of function in the determination of impairment rating. This is defined as a “consensus-derived percentage estimate of loss of activity reflecting severity for a given health condition, and degree of associated limitations in terms of ADLs [italics added].”

This chapter is not meant to provide the reader with the necessary skills to do actual impairment ratings, which can be fairly complex and detailed. However, a brief sketch of the approach to impairment rating based on the latest AMA Guides is given here ⁴⁸:

• There are four impairment criteria defined within the AMA Guides, with some clarification given for each criterion:

1. History of clinical presentation (the overall clinical diagnosis)

2. Physical examination (physical examination findings at the time of impairment rating)

3. Clinical studies and objective tests (e.g., imaging studies, blood work, and electrodiagnostic studies)

4. Functional assessment or history (self-reported ability to function from the patient, with a functional assessment scale preferably used such as the Pain Disability Questionnaire)

• In assigning a claimant to an impairment class, the physician relies upon a “key factor,” one of the four impairment criteria listed above. Typically the key factor leading to a claimant’s assignment to a particular class is the diagnosis (i.e., history of clinical presentation). However, a different key factor, such as diagnostic testing for cardiac conditions, might be relied upon for different organ systems. Each impairment class is associated with a range of possible whole-person impairment percentages.

• To arrive at a precise percentage of whole-person impairment, the examiner fine tunes the impairment rating by assigning an impairment grade within the assigned class. Grades range from A (when claimants are substantially less impaired than most people in their impairment class) to C (when the degree of impairment of claimants is average for people with their impairment grade) to E (when claimants are substantially more impaired than most people in their impairment class). The “default grade” is C; this is the grade that an examining physician should assign when there is no compelling evidence to support a higher or lower grade.

• To determine a claimant’s impairment grade, the examiner relies upon the “non–key factor” impairment criteria. Given that the key factor is generally the diagnosis (history of clinical presentation), these other criteria are physical examination findings, clinical studies, and functional history. If these impairment criteria suggest more severe impairment than the class chosen by use of the key factor, the examiner cannot change the chosen class; however, the examiner can choose a higher grade within the class (i.e., grade D or E), resulting in a relatively higher whole-person impairment. In the example of a cervical spine impairment rating for intervertebral disk herniation or documented alteration of motion segment integrity (AOMSI), there are five impairment classes (Table 6-1).

• Class 2 for the cervical spine example given here is for “intervertebral disk herniation and/or AOMSI at a single level with medically documented findings; with or without surgery AND with documented radiculopathy at the clinically appropriate level present at the time of examination.”

• More severe related cervical spine disorders are rated class 3 or 4 (e.g., multilevel active radiculopathy), and less severe cervical spine disorders are given class 0 or 1 (e.g., resolution of radiculopathy).

Table 6-1 Simplification of AMA Guide’s Cervical Spine Regional Grid for Impairment Rating

Note that there is a new emphasis on functional history with this edition of the AMA Guides. Loss of function is assessed in part by self-report measures that claimants may fill out at the time of their impairment evaluations. Different measures are used for different kinds of disorders; for example, the QuickDASH is used for disorders of the hand, while the Pain Disability Questionnaire is used for evaluating functional limitations involving the spine. The important general point is that impairment ratings in the AMA Guides sixth edition incorporate subjective information from claimants about their burden of illness. The significance of this change in the Guides is modest, however, because functional history plays a relatively minor role, modulating the grade within a given class. The primary emphasis in the Guides continues to be on objective findings rather than subjective history in the impairment rating process.

Further Thoughts on Impairment Versus Disability

Disability agencies typically assume a strong linkage between impairment and disability and assume that impairment is a necessary condition for disability. The logic underlying this requirement is straightforward. Disability programs are designed to assist individuals who are unable to compete in the workplace because of a medical condition. In essence, disability programs attempt to partition individuals who fail in the workplace into two broad groups: those who fail because of a medical condition, and those who fail for other nonmedical reasons. There are many potential nonmedical reasons, including a lack of demand for their skills or a lack of motivation. Disability programs require evidence that applicants have a medical problem underlying their workplace absence. Impairment provides the needed evidence, because it can be viewed as a marker that individuals have a medical problem that diminishes their capability. Conversely, if individuals have no identifiable impairment, they are assumed to have no workplace limitations caused by a medical condition.

Disability agencies typically assume that the severity of patients’ impairments correlates with the degree and/or probability of their being disabled from work. Even when an agency compensates for work disability and not for impairment, it will often seek information about a patient’s impairment to rationalize its decision about whether to award disability benefits. As will be discussed, the assumption that increasing impairment leads to increased disability can be challenged when quantifying impairment. Certainly the linear correlation between the level of disability and impairment is often absent. Physiatrists should educate others, including case managers, physicians, and attorneys when applicable, about these imperfections.

Whereas it is possible to distinguish conceptually between impairment and disability, the distinction is not always clear in many practical situations. For example, the notion of a measurably dysfunctional organ does not readily apply to psychiatric impairments. Although the distinction between impairment and disability is easy to make in some medical conditions, it is difficult to make in others.

Another problem is that the correlation between severity of impairment and severity of disability is far from perfect, as illustrated in the following examples:

• A patient might have serious impairment yet very little apparent vocational disability. A striking example is that of the world-famous physics professor, Dr. Stephen Hawking. He is incapacitated from the most basic ADLs because of motor neuron disease, and would qualify for a very high total body impairment according to the AMA Guides. However, he is not work disabled. In fact, he has remained active as a theoretic physicist of international acclaim well beyond the onset of motor neuron disease in his 20s. Within the ICF framework, Dr. Hawking would have almost complete activity limitations, but notably fewer work-related participation restrictions.

• A patient might have a very mild ratable impairment, as measured through the AMA Guides, from a lumbar or cervical facet injury as a result of a motor vehicle crash. However, such an injury can cause devastating vocational consequences if the patient has a job that requires constant heavy physical labor. Such a patient might even be rated as having “no impairment” according to some examiners, because of a lack of a demonstrable disk herniation with advanced imaging or a lack of radicular findings on examination, or both. When subjected to a functional capacity evaluation, the patient might be shown to be truly incapable of doing heavy physical labor. Consequently, such a patient could be considered 100% disabled from such labor and yet might have little or no ratable impairment according to some examiners’ interpretations of impairment rating guidelines.

• A patient might have had a demonstrable disk herniation with radiculopathy and responded well to spinal surgery. According to both the AMA Guides and a number of workers’ compensation guidelines, this patient would have significant whole-body impairment. Despite this impressive level of impairment, this patient might have little or no disability in terms of work role and ADLs.

• As a final example, the patient could have a well-defined impairment—amputation of the fifth digit of the nondominant hand. This type of amputation is very well described in the AMA Guides, but the patient’s disability, if any, will be strongly dependent on the patient’s profession. If the patient were a concert pianist, the disability might be 100%. If the patient were a psychiatrist, there would likely be no disability. If the patient were a construction worker, the disability would likely be minimal, mild, or possibly moderate, depending on the individual tasks that had to be performed.

Roles of Physicians in Disability Evaluation

Some physicians become expert in disability evaluation and make disability evaluation a central part of their clinical practices. Some function as consultants to other physicians when they perform disability evaluations. Other physicians with an interest in disability evaluation perform independent medical examinations (IMEs) that are commissioned by insurance carriers, disability agencies, or attorneys. Still others work as employees of disability agencies or insurance companies. As part of this work, they might perform disability evaluations by directly examining claimants. More typically, however, such consultants play a variety of indirect roles—for example, advising claims managers when to order IMEs, or reviewing IMEs that have been performed.

Many physicians do not seek opportunities to perform disability evaluations because they are uncomfortable evaluating disability in patients whom they are treating. They correctly perceive that the process of disability evaluation places a physician between the interests of the patient and those of an insurance company or disability agency. In the best of circumstances, this can seem to the physician like trying to fit a round peg into a square hole, because the categories of disability established by such agencies often do not match the clinical realities of patients.

In the worst case, clinicians end up feeling caught in the crossfire between adversaries. They may perceive employees of disability agencies as unenlightened bureaucrats who make excessive demands for documentation. On the other hand, they may perceive their patient as reporting excessive incapacitation and trying to enlist physicians as allies in their battle to legitimize their disability.

The concerns that treating physicians have about doing disability evaluations appear to fall into two categories: knowledge deficits and ethical concerns. Physicians who work primarily as clinicians are likely to be unfamiliar with the disability laws and regulations relevant to their patients, and the disability agencies that administer them. They are also likely to lack expertise in the mechanics of rating impairment, such as those detailed in the AMA Guides,⁴⁸ and in the methods that can be used to assess work ability.^20,^21,^31,^33,⁴⁹

Treating physicians can be concerned about conflicts between the clinical role they normally play when they treat patients and the adjudicative role that is required during a disability evaluation. Informal observation as well as examination of the limited literature on these roles ^26,^42,^58,⁶⁵ suggests several differences between the two roles. For example, physicians performing disability evaluations are expected to focus on objective findings and legal responsibility, including causation, for an examinee’s disorder, but these are not the main concern of physicians when they provide clinical treatment.⁴⁶ As Sullivan and Loeser⁵⁸ have noted, significant ethical issues arise when physicians switch back and forth between these two roles.

Assessing Self-Reports of Patients Regarding Physical Capacity

A key challenge is to combine examinees’ self-reports regarding their incapacitation with objective medical information relevant to their injury.⁴⁷ Note that the definition of “objective medical information” is not always clear. Unfortunately the existence of objective medical findings often depends on the degree to which technologies have advanced. For example, before myelography became available, radiographic studies (i.e., x-ray films) did not demonstrate objective findings for patients with radiculopathies.

A second problem is that a high level of interrater reliability is a necessary condition for objectivity in any endeavor. However, in the arena of impairment and disability evaluation, it is common for different examiners—many of whom consider themselves to be “forensic experts”—to generate disparate conclusions about the same patient.

One way for a physician to resolve potential discrepancies between self-report data and objective findings is to accept at face value what patients say about their physical capacities. A physician adopting this strategy would run the risk of underestimating the rehabilitation potential of individuals who overstate their incapacitation either deliberately, as in the case of malingerers, or as a result of genuine misperceptions regarding their abilities. At the opposite extreme, a physician might make decisions about the disability status of patients strictly on the basis of what they perceive to be “objective findings,” and react skeptically to reports of incapacitation that are not closely linked to these findings.

A position somewhere between these two extremes is probably most appropriate. The perceptions that patients have about their abilities certainly should not be ignored or discounted. As a practical matter, research demonstrates that these self-appraisals are important predictors of whether patients with pain problems will perform well on physical tests or will succeed in terminating their disability, or both.^14,^15,²³^–²⁵ ^,30 Physicians who make disability decisions without considering patients’ appraisals are discarding valuable data. As a result, their decisions can go awry in two ways. First, they can pressure patients to return to work in jobs that the patients are realistically not capable of performing. Second, they can be ineffective in resolving disability issues. Consider patients who are released to work by their treating physician or by an independent medical examiner even though they are convinced that they are unable to work. Such patients are likely to retain an attorney and start a protracted legal battle regarding their work status.

But the fact that patients’ perceptions are important does not mean that they are valid or immutable. In fact, research on patients with disability related to chronic pain suggests the opposite: some often have distorted views of their capabilities, and these views are modifiable.^1,^12,^28,³⁵ Disability evaluators need to consider the validity of a patient’s stated activity limitations in light of the biomedical information available and their assessment of the patient’s credibility. Evaluators should reserve the right to challenge the patient’s self-assessments and to make decisions that are discordant with these assessments.

In summary, the treating physician should carefully assess examinees’ perceptions regarding their ability to perform various tasks and, whenever feasible, should take them into account when rendering judgments about their ability to work. But the physician should not let examinees control the discussion about disability. Instead, physicians should be ready to challenge the appraisals of examinees when they believe them to be inaccurate.