Background and Purpose: Although the modified Rankin Score (mRS) is broadly used as a measure of stroke outcome, quality of life (QOL), expressed in 0-1 numerical utility values (0=death, 1=perfect health), more accurately reflects patients’ value for particular health states. 3 methods for eliciting utility include: visual analog scale (VAS), standard gamble (SG) and time trade-off (TTO). SG, considered the classic method for obtaining utilities, involves making decisions under uncertainty or risk. We hypothesized that utilities from standard gamble (SG) would be systematically different than TTO & VAS and utility values would not be linearly associated with mRS scores.
Methods: Utilities were elicited from ischemic stroke patients or proxy family members in the ARTSS-2 randomized trial; clinicaltrials.gov/NCT01464788. A societal perspective was performed using TTO (EuroQol-5D) and 2 patient-centered utility methods: VAS, a “feeling thermometer” and the SG. Certified raters blinded to utilities assessed 90-day mRS. Mean utilities were mapped across the mRS. As SG can be cognitively complex, requiring simultaneous assessments of both benefit and harm, patients’ capacity was determined using the validated Assessment of Capacity Evaluation. Only patients demonstrated capacity were able to perform the QOL evaluations.
Results: 86 of 90 (96%) patients had utilities at 90-days. Excluding missing and deaths, 70 patients had utilities generated by either the patient (N=48; 70%) or the proxy (N=22; 30%). TTO and VAS utilities declined in a non-linear fashion with increasing mRS. In general, SG utilities were larger and varied the least across mRS (Figure).
Conclusions: Patient elicited standard gamble utilities of stroke health states do not appear to correlate with the mRS. Further research is necessary to understand divergence between SG and other methods of QOL elicitation in stroke patients.