Exploring the origin and conceptual framework of the EQ VAS.

Purpose: The objective of this paper is to report on the origin of the EQ VAS and current understanding of the EQ VAS conceptual framework via a literature search based on the snowball approach.

Methods: A review was conducted in two steps: (1) a citation search and (2) a search of the EuroQol group's grey literature.

Results: The findings indicate that the EQ VAS was originally designed as a warm-up task for valuing hypothetical health states. The characters of the EQ VAS reflect its valuation origin, such as drawing a line (the previous version), vertical orientation, and choice of end labels. None of these design elements of the EQ VAS were chosen for the purpose of measuring self-reported overall health. Despite this, the EQ VAS proves to be a valid self-reported health status measure with its psychometric properties demonstrated in various general and clinical populations. We found a dearth of literature addressing the conceptual framework of EQ VAS as a measure of self-rated overall health.

Conclusion: With its potential as a powerful measure of overall health, further research into EQ VAS design, conceptual framework and empirical function is warranted.