Validation of disability categories derived from Health Utilities Index Mark 3 scores

To establish empirical evidence for the validity of the following disability categories derived from Health Utilities Index Mark III (HUI3) global utility scores: none (1.00), mild (0.89 to 0.99), moderate (0.70 to 0.88), and severe (less than 0.70).

Data from the 2005 Canadian Community Health Survey (cycle 3.1) were analyzed. Frequency distributions, stratum-specific likelihood ratios, and multinomial regression were used to examine the relationship between health indicators and the HUI3 disability categories.

People reporting chronic conditions, activity restrictions, and fair/poor self-rated health (general and mental) were more likely to be in the moderate and severe disability categories. Those having more positive outcomes on the health indicators tended to fall into the mild and no disability groups. The stratum-specific likelihood ratios increased monotonically with the severity of disability level. Compared to those with positive health status characteristics, those with negative health status characteristics had the highest odds of falling in the severe rather than the non-disabled category.

This study makes an initial contribution to the evidence base for the validity of the proposed HUI3 disability categories. The categories were well-supported empirically and are likely to be useful for assessing disability levels.