Health State Utilities for Achondroplasia: A Time Trade-Off Study

Achondroplasia is a rare genetic disorder that prevents the changing of cartilage to bone, leading to disproportionate short stature, which can have serious complications that affect quality of life. The aim of this study is to elicit health state utility values (HSUVs) corresponding to health states (HSs) describing the impact of achondroplasia, via a time trade-off valuation approach with the general public.

Ten HSs were defined for this time trade-off exercise. A pair of HSs (no major complications or complications) were created for the following age groups: younger than 2 years (HS1), 2 to 4 years (HS2), 5 to 14 years (HS3), 15 to 18 years (HS4), and older than 18 (HS5). Interviews were conducted face to face with a moderator in the United Kingdom and United States. Descriptive statistics were computed for HSUV and the differences tested using paired student's t tests.

In total, 420 respondents were recruited; after quality checks, the sample for analysis totaled 354. The highest HSUVs were for the 2 youngest states (HS1;HS2), without major complications, with mean values of 0.73 (SD 0.39) and 0.76 (SD 0.34), respectively. The lowest mean HSUVs were for the 2 oldest states, with complications (HS4;HS5), eliciting mean values of 0.55 (SD 0.36) and 0.55 (SD 0.34), respectively. Differences for complication states within age group pairs ("child 5-14," "teenager 15-18," "adult > 18") were statistically significant (P < .05).

Overall, HSUVs for achondroplasia were lower than for the normative population across their lifetime. Differences between HSUVs were seen between age groups, with complications reducing the mean utility valuations further, particularly in older people with achondroplasia.