Permanent Impairment—Disability Rating Study: Impact of the AMA Guides on Permanent Disability Ratings in the State of California
Christopher R Brigham
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Dave Bellusci
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Terry Beuret
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Following passage of California Senate Bill No. 899 (SB 899) in 2005, disability in California is rated using the AMA Guides to the Evaluation of Permanent Impairment, (AMA Guides), Fifth Edition. The authors compare the disability ratings under the new law to those under the pre-2005 California Permanent Disability Rating Schedule. The authors reviewed 267 cases, of which 250 were ratable, and the ratings of expert reviewers who used the AMA Guides were compared with the ratings of the pre-2005 evaluations (the reviewers who used the AMA Guides to examine the earlier evaluations were blinded to the results of the earlier evaluations). The average permanent disability ratings were 22% under the old schedule and 6.4% under the new schedule, possibly because the current AMA Guides bases impairment primarily on objective data, not subjective complaints and opinions regarding work restrictions. The AMA Guides also has changed certain tests and minimized others (eg, range of motion and grip, respectively). Study limitations include sample selection and differences between pre-2005 evaluators and the highly proficient experts who used the AMA Guides for the present study. The authors conclude that this study shows ratings that are lower than those typically given by treating physicians and other examiners, and they note potential causes of the discrepancies, including evaluation by physicians who are not yet expert and experienced in using the AMA Guides.

  • 1.

    President, Brigham and Associates, Inc. Portland, Maine, and San Diego, California.

  • 2.

    Senior Vice President and Chief Actuary, Workers Compensation Insurance Rating Bureau, San Francisco, California.

  • 3.

    Psychologist, Kailua, Hawaii.

  • 4.

    SB 899, which was enacted effective April 19, 2004, included a set of comprehensive reforms to the workers' compensation benefit delivery system in California.

  • 5.

    California Labor Code Section 4660 provides that the schedule is to take into account an employee's diminished future earning capacity based at least on part from the evaluation of California's Permanent Rating Schedule Interim Report (December 2003) prepared by the RAND Institute for Civil Justice.

  • 6.

    Based on database of reviews performed by Brigham and Associates, Inc, upon request of clients. Note these referrals often are made based on concern that a rating is erroneous; therefore, this may not reflect all ratings performed. “Observed” refers to the values provided by the original rating physician and “Expert Re-Rating” refers to values obtained based on expert review of the clinical data and application of AMA Guides criteria.

  • 7.

    Results of “Study of the Impact on Changing from the AMA Guides to the Evaluation of Permanent Impairment, Third Edition Revised to the Fourth or Fifth Editions in Determining Workers' Compensation Impairment Ratings” performed at the request of Department of Labor and Employment, The State of Colorado by Christopher R. Brigham, MD (

  • 8.

    State of Texas Designated Doctor Study, courtesy of William Nemeth, MD. Note this is based on the use of the Fourth Edition.

  • 9.

    Impairment Values for specific regions of the body were determined by assigning a specific ICD-9-CM code to each body portion rated and then grouping of the ICD-9-CM codes.

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