Bridging and Validation of the Specific Graves' Ophthalmopathy Quality of Life (GO-QOL) Questionnaire with Health State Utility Values.

OBJECTIVE: In thyroid eye disease (TED) inflammation and expansion of orbital muscle and peri-orbital fat produce diplopia and proptosis, severely impacting patient quality of life (QOL). Reported heath state utility (HSU) scores, which are QOL measures, allow quantification of TED impact and improvement with therapies; however, no current QOL instrument has been validated with HSU scores for TED. Here we use disease-specific Graves' ophthalmopathy (GO)-QOL questionnaire and HSU scores to validate QOL impact.

METHODS: GO-QOL scores from patients in two randomized, masked, placebo-controlled teprotumumab trials (N=171) were compared with 6 HSU values based on severity of proptosis/diplopia in those studies. Patient GO-QOL and HSU scores were compared at baseline and following 6-month treatment via regression analyses. GO-QOL and HSU scores were correlated for validation and quantification of QOL impact by severity state and estimate quality-adjusted life-year (QALY) improvement.

RESULTS: GO-QOL scores were correlated with TED severity indicating worse severity was associated with lower (worse) GO-QOL scores. Less severe health states were represented by higher (better) GO-QOL scores. Importantly, GO-QOL scores were positively correlated with utility scores of the 6 health states allowing for conversion of the GO-QOL scores to utility scores. A positive (improved) 0.013 utility change was found for each 1-point (positive) improvement in GO-QOL produced by teprotumumab versus placebo.

CONCLUSION: Patients with moderate-severe active TED health states demonstrate increasing TED severity associated with declining utility values and worsening GO-QOL scores. These results indicate GO-QOL scores can be used to bridge to health state utility scores for benefit quantification.