HEALTH UTILITIES OF RARE HERITABLE DISORDERS: APPROACHES FOR HEALTH STATE DESCRIPTIONS AND MEASURING SPILLOVER EFFECTS ON FAMILY MEMBERS

Purpose:  Measure effects on health-related quality of life (HRQOL) for three heritable disorders (phenylketonuria (PKU), Pompe disease, Krabbe disease) on patients and their families.

Methods:  Respondents were asked to value health utility using time trade-off questions for hypothetical health state descriptions for differing levels of severity of PKU, Pompe, and Krabbe diseases.  Descriptions varied by age of the patient (infant, child, adult).  Valuation questions used three frames: valuing the scenario for one's self; for a hypothetical child; and as a family member of the child (spillover effect). For the spillover frame, respondents were asked to consider effects of the child or infant's condition on their own HRQOL. A novel feature of this study was the inclusion of whiteboard animation videos in addition to the text description for each health state to assist respondents' understanding.  Respondents were drawn from a nationally representative online sample, the GfK Knowledge Panel, and reflected characteristics of the general US adult population (n=865).  Primary outcomes were descriptive statistics for health utilities.  Regression analyses were used to evaluate the effect of respondent characteristics on time trade-off amounts. Levene's test was used to evaluate differences in the standard deviation of health utilities for respondents who viewed the videos compared to those that did not.

Results:   For severe forms of PKU, Pompe, and Krabbe, the mean health utilities ranged from 0.38 (SE: 0.03) for advanced infantile Krabbe to 0.68 (SE: 0.03) for less adherent adults with PKU. Milder forms of the conditions ranged from 0.47 (SE: 0.03) for early stage infantile Krabbe to 0.81 (SE: 0.02) for more adherent adults with PKU. HRQOL spillover effects on family members also varied with the severity of the family member's health state, ranging from 0.81 to 0.93. 42% of respondents clicked through to view the videos.  Mean health utilities were not significantly different for video-viewers compared with non-video-viewers, however, the standard deviation of the health utility was smaller among those who accessed the videos (0.36) compared to those who did not (0.39; p-Value: <0.001).

 

Conclusion:  These rare conditions have a substantial impact on HRQOL for patients and a measurable impact on family members' HRQOL. The health utilities reported in this study can be used to inform cost-effectiveness analyses of newborn screening programs to identify these conditions.