Objective: U.S. Disability Systems share a common procedural approach to the determination of disability for purposes of compensation. The structural and anatomical consequences of the injury or disease are defined and measured according to medical impairment, which is used to estimate the individual's loss in terms of their capacity to perform activities of daily living (ADLs) and, presumptively, their losses in terms of vocational and non-vocational pursuits and quality of life. The physician is traditionally empowered to rate the severity of impairment in terms of a percentage loss to the "whole person" and according to criteria specific to each disability system. Often, the impairment percentage so derived, then is directly translated into a monetary sum for purposes of compensating these losses. The AMA periodically publishes and updates a physician impairment rating guide (the AMA Guides). The 6th Edition, published in 2008, incorporates the definitions and terminology of the ICF and provides a simple means of assessment of ADLs as part of the rating process. It also has shifted the ratings criteria towards a diagnosis-based approach, ostensibly to improve inter-rater consistency and reliability.
Conclusion: Further work is needed to refine and validate ADL-based functional assessment tools applicable to medical impairment ratings, and to demonstrate the levels of consistency and reliability of the new rating method. Of equal importance, operational standardization across systems is also needed to enable common criteria and metrics to be developed and applied when determining the non-medical aspects of disability according to vocational and non-vocational pursuits and quality of life. Impairment ratings cannot be optimally designed to serve as the singular determinant of, nor be held solely accountable for, the disability awards.