Mapping the mRS Into the EQ-5D-5L in Patients With Ischemic Stroke

BACKGROUND: 

– Mapping concerns the cross-walking of one health-related quality of life instrument to another. This study aimed to translate the modified Rankin Scale (mRS) score at 3 months after ischemic stroke into 5-level version of the EQ-5D (EQ-5D-5L)–based utility values, which may be used for the derivation of quality-adjusted life years for cost-effectiveness analyses. 

METHODS:

– Data from 3 Dutch multicenter phase III clinical trials in ischemic stroke were pooled (MR CLEAN [Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands]-NO-IV, MR CLEAN-MED, and MR CLEAN-LATE). The mRS and EQ-5D-5L were assessed by telephone interview at 3 months poststroke. The correlation (Spearman coefficient) between the mRS and each EQ-5D-5L domain was assessed. Various direct and indirect mapping algorithms were explored. Model performance (predictive ability) was assessed using bootstrapping in the full testing set (mRS score 0–5) and in patients with independent (0–2) and dependent (3–5) mRS scores separately. Results were validated in an external validation set derived from a cross-sectional Dutch study. Final utility estimates per mRS score were assessed in the pooled trial and external validation data set. 

RESULTS: 

– The EQ-5D-5L dimensions self-care, daily activities, and mobility demonstrated the strongest correlation to the mRS (ρ=0.46–0.70). Correlation coefficients of the pain and anxiety dimensions were relatively poor (ρ=0.37–0.45). Indirect mapping with a multinomial logit model was identified as the preferred mapping algorithm. In the pooled data set, the median (interquartile range) age was 71 (62–79), and 56% of patients were male. Mean (SD) fitted utility values per mRS score were; mRS score 0: 0.947 (0.004); mRS score 1: 0.860 (0.009); mRS score 2: 0.758 (0.013); mRS score 3: 0.597 (0.017); mRS score 4: 0.352 (0.017); and mRS score 5: 0.147 (0.017). 

CONCLUSIONS:

– The mean utility weights provided in this study may be used for the direct estimation of quality-adjusted life years from mRS scores. Furthermore, the multinomial logit model may be used to derive utility values from new data sets with different country-specific utility tariffs. Our results are ideally suited for application in cost-effectiveness analyses.