The extent to which common health-related quality of life indices capture constructs beyond symptoms and function

Abstract

Purpose: This study proposes to identify for 5 widely used generic HRQL and QOL measures the extent to which function and global feelings of well-being are represented in their content.

Methods: The 5 indices were the EQ-5D, the HUI, the SF-36, SF-12, and the WHOQOL-Bref. A total of 15 raters with a variety of health and research backgrounds mapped the items. Raters independently identified all codes that could possibly map to the item and indicated the code that best reflected the underlying intent of the item, using the standardized mapping rules and methodology. A Delphi process aided consensus for each of the items. The consensus rounds involved reconsideration of item codes for which 70% of raters did not agree on the "best" code. These consensus rounds were terminated when item codes reached the threshold of 70% agreement or when it became evident from that consensus would not be reached.

Results: Function was a predominant construct for the 5 indices, with the proportion of items capturing function ranging from a low of 27% for the WHOQOL-Bref to a high of 92% for the SF-12. Less than 50% of items within the indices mapped to the granularity of function as described by the ICF.

Conclusions: This paper demonstrates an additional method to validate the content of health-related indices to supplement the qualitative methods of consulting with experts and patients.