Abstract
Despite the Occupational Safety and Health Act (OSHA) and other legislation enacted to help prevent occupational hearing loss, noise-induced hearing impairment still occurs. Otolaryngologists are called upon frequently to evaluate claimants who allege that they have suffered work-related hearing impairment. Physicians are involved not only in confirming or refuting the presence of hearing loss, but also in diagnosing its cause and helping to determine the degree to which it might have impacted a person's life or caused disability.
Fortunately for everyone concerned, physicians do not have to depend on individual experience and unsubstantiated opinion to make such judgments. The medical and scientific community has nationally (and in some cases internationally) accepted standards to guide such judgments so that they can be as valid, reliable, fair, and consistent as possible across individuals, geographical locations, and even organ systems. All physicians involved with evaluations of impairment and disability should be familiar with the American Medical Associations (AMA's) Guides to the Evaluation of Permanent Impairment 1 in order to be able to comply with the standard of care.
It is important to understand the Guides in historical context in order to appreciate the value of this dynamic book and its importance as a scientific compendium. In the United States, physicians from all specialties have been developing and refining the Guides for more than half a century. The AMA established an ad hoc committee in 1956 that led to a publication in the Journal of the American Medical Association (JAMA) in 1958 called “A guide to the evaluation of permanent impairment of the extremities and back.” 2 By 1970, a total of 13 such Guides had appeared in JAMA. They were collected as a compendium in 1971 and published as the first edition of the Guides. 3 The value and importance of the Guides became apparent, and great effort has been devoted to revising and improving the book.
In 1981, the AMA established 12 expert panels in preparation for the second edition, which was published in 1984. The third (1988), fourth (1993), fifth (2000), and sixth (2008) editions all contained important changes, many of which are summarized in the introductory chapters of each edition. However, the most striking changes were promulgated throughout the sixth edition, to which I was privileged to contribute as lead author for the otolaryngology chapter.
I had followed the process for many years through my father, Joseph Sataloff, MD, who was a contributor or chapter editor for otolaryngology for the second through fifth editions. I also serve as the American Academy of Otolaryngology-Head and Neck Surgery's (AAO-HNS) Advisory Committee Representative to the AMA for Evaluation of Permanent Impairment. This commentary reviews some of the valuable perspective gained through these activities. It is hoped that the insights summarized briefly herein will assist clinicians, attorneys, and others in understanding the genesis of the Guides, and the importance of their proper application.
As scientific knowledge and methodology expand and our knowledge base grows, it is essential for physicians and scientists to incorporate new knowledge and allow our practices to evolve. The Guides have been strikingly successful in this regard, especially the most recent edition. It warrants discussion because it has some fundamental differences from the first five editions, with which all otolaryngologists should be familiar. Each new edition has incorporated the latest scientific research and practice.
The first five editions provided the best available information for evaluating permanent impairment, but they had some shortcomings that were acknowledged by most of the scientific community, including by those involved in writing the Guides. The sixth edition incorporates a radical paradigm shift to a simplified, function-based, internally consistent model of disablement that has rectified many of the concerns about earlier editions. The new approach involves using the internationally accepted International Classification of Functioning, Disability and Health (ICF). 4 The latest edition of the Guides also focuses more directly on diagnosis, using evidence-based medicine when possible; simplicity to optimize inter-rater and intra-rater reliability; functionally based ratings percentages; and consistent conceptual and methodologic approaches and ratings across organ systems.
The ICF model is a comprehensive classification for describing and measuring health and disability in individuals and populations. It assesses bodily functions and structures (including impairments), activity (including activity limitations), and participation in life situations (including participation restrictions). It relates the health condition of an individual to environmental and personal factors. This internationally accepted approach represents a major improvement toward which contributors to the Guides have been striving for many years. Developing the ICF model was a complex process, and it was not complete by the time the fifth edition was printed.
The ICF arose from a worldwide consensus process, was endorsed by the World Health Assembly in 2001, 5 and has been accepted as a member of the World Health Organization family of international classifications. The AMA's Guides has now adopted ICF terminology and definitions and used this approach to refine evaluation of impairment, disability, and impairment rating. This approach has created greater consistency within and between organ systems and established impairment and disability classifications based on the latest available evidence and expert consensus. Emphasis was placed on precision, accuracy, reliability, and validity. However, evaluation of functional impact was enhanced using the 5-point scale taxonomy created by the ICF. The approach allows incorporation of information from the history, physical findings, objective test results, functional assessment, and determining the burden of treatment compliance when appropriate.
The revision process for each chapter in the Guides is not only rigorous, but also multidisciplinary. For example, contributors to the otolaryngology chapter included not only otolaryngologists, but also physicians in other specialties such as occupational and environmental medicine and pulmonology. As an example, all aspects of the otolaryngology chapter were reexamined and researched during the revision process. Literature was searched for new evidence and new consensus opinions, and the content of our chapter was compared with overlapping content in other chapters to optimize consistency across organ systems.
This revision effort included reviewing the formula used for calculating hearing impairment. The original approach to this problem was published in 1959. 6 That formula used 500 Hz, 1,000 Hz, and 2,000 Hz. Based on additional study, the formula was revised to include 3,000 Hz in 1979. 7 Higher frequencies are not included because they are not necessary to understand speech. For example, most early telephones used through the 1960s did not transmit frequencies above 2,800 Hz through their earpieces, and speech comprehension on those devices was not problematic.
Since 1979, considerable conjecture and opinion have been promulgated supporting the formula as it stands8-14 and advocating changes 15 in the formula; and there has been vast experience in applying it for more than 30 years. After reassessment of available data, the relevant committees of the AAO-HNS, as well as other expert clinicians and the authors of the otolaryngology chapter in the sixth edition of the Guides, have found no credible evidence to support revising the formula again. In addition, the consensus and evidence still indicate that pure-tone audiometry is the most appropriate test in this population for estimating an individual's ability to hear speech. While other audiometric tests can be used in the diagnostic process, measures such as the discrimination score can be manipulated so easily that they cannot be considered a valid standard for routine determination of hearing performance in medicolegal settings. Consequently, the AAO-HNS formula remains the basis for the formula in the AMA Guides.
As a result of the exceedingly rigorous scientific process through which the Guides was developed and has evolved, the publication has been recognized and accepted nationally. In nearly all U.S. territories, states, and commonwealths, the AMA's Guides is either recommended or mandated for use by Workers’ Compensation law. It is also used for actions involving the Federal Employees’ Compensation Act, Longshore and Harbor Workers’ Compensation Act, and Federal Employees’ Compensation laws. AMA's Guides to the Evaluation of Impairment is the premier compendium of scientific evidence and expert opinion related to the topic and has been accepted as establishing the standard of care by the AMA and essentially all major specialty societies in the United States (including the AAO-HNS).
Physicians involved with patients being assessed for possible noise-induced or other work-related hearing impairment should be not only loosely familiar with the Guides from past editions, but also current on the latest scientific and methodologic advances in the most recent edition of this definitive reference.