Comparative Analysis of Impairment Ratings From the 5th to 6th Editions of the AMA Guides

OBJECTIVE: The association of American Medical Association's (AMA) Guides edition with impairment ratings is uncertain. METHODS: We used data from a consecutive sample of 249 injured workers referred for an independent evaluation 10 months before and after assessors switched from the 5th to the 6th edition of the AMA Guides. RESULTS: The median whole person impairment rating was 7.0% (interquartile range [IQR]: 4 to 14) for 131 claimants assessed with the 5th edition of the Guides, and 4.0% (IQR: 2 to 8) for 118 claimants assessed with the 6th edition (P-value for difference: 0.002). Multivariable analysis showed a 36.4% relative reduction (95% confidence interval [CI] 17.2% to 57.3%) in impairment rating with the 6th edition of the Guides versus the 5th edition. CONCLUSIONS: The 6th edition of the AMA Guides provides systematically lower impairment ratings for injured workers than the 5th edition.