Choosing the Best Instrument for Measuring Health Spillover Effect in Caregivers of Patients With Multiple Sclerosis

To measure the health spillover effect in caregivers of patients with multiple sclerosis (MS), we aimed to select the best instrument from 2 common health-related quality of life (QoL) instruments, the 3-level EQ-5D (EQ-5D-3L) and the Health Utilities Index Mark 3 (HUI-3), by assessing them.

Using consecutive sampling, 452 primary caregivers of patients with MS were asked to fill out a Care-related QoL instrument (CarerQol-7D), EQ-5D-3L, HUI-3, and the Center for Epidemiologic Studies Depression Scale between October 2019 and May 2020. Convergent and clinical validity were assessed to measure spillover effect in caregivers of patients with MS.

A strong correlation of health-utility scores between EQ-5D-3L and HUI-3 (r = 0.914, P < .01) was observed. The 95% limit of agreement (LoA) for CarerQol-7D and HUI-3 (-10.6 to 8.2) was narrower than the LoA for CarerQol-7D and EQ-5D-3L (-15.1 to 17.1). Both EQ-5D-3L and HUI-3 proved clinical validity for the QoL of caregivers. The CarerQoL-7D score was significantly lower in female (P < .001), single (P < .014), lower-educated (P < .001), parent's relatives (P < .001), and unemployed (P < .001) caregivers.

We found that both, EQ-5D-3L and HUI-3, were appropriate for measuring caregivers' QoL, although HUI-3 was a better choice because of its narrower LoA. Our findings suggest researchers should use HUI-3 to measure the quality-adjusted life-year of caregivers to aggregate with the QoL of patients in the denominator of an economic evaluation equation, such as the cost-effective ratio.