Comparison of the flexible parametric survival model and Cox model in estimating Markov transition probabilities using real-world data.

BACKGROUND AND OBJECTIVE: Markov micro-simulation models are being increasingly used in health economic evaluations. An important feature of the Markov micro-simulation model is its ability to consider transition probabilities of heterogeneous subgroups with different risk profiles. A survival analysis is generally performed to accurately estimate the transition probabilities associated with the risk profiles. This study aimed to apply a flexible parametric survival model (FPSM) to estimate individual transition probabilities. MATERIALS AND METHODS: The data were obtained from a cohort study investigating ischemic stroke outcomes in Western China. In total, 585 subjects were included in the analysis. To explore the goodness of fit of the FPSM, we compared the estimated hazard ratios and baseline cumulative hazards, both of which are necessary to the calculate individual transition probabilities, and the Markov micro-simulation models constructed using the FPSM and Cox model to determine the validity of the two Markov micro-simulation models and cost-effectiveness results. RESULTS: The flexible parametric proportional hazards model produced hazard ratio and baseline cumulative hazard estimates that were similar to those obtained using the Cox proportional hazards model. The simulated cumulative incidence of recurrent ischemic stroke and 5-years cost-effectiveness of Incremental cost-effectiveness Ratios (ICERs) were also similar using the two approaches. A discrepancy in the results was evident between the 5-years cost-effectiveness and the 10-years cost-effectiveness of ICERs, which were approximately 0.9 million (China Yuan) and 0.5 million (China Yuan), respectively. CONCLUSIONS: The flexible parametric survival model represents a good approach for estimating individual transition probabilities for a Markov micro-simulation model.

[Health Utility of Patients with Stroke Measured by EQ-5D and SF-6D].

OBJECTIVE: To compare EQ-5D and SF-6D for measuring health utility of stroke patients in health economic evaluation studies. METHODS: A prospective cohort study was conducted on 596 stroke patients in the West China Hospital of Sichuan University from 2010 to 2016. Data were collected at baseline through face to face interviews and at the follow-up stages through telephone interviews with a three-month interval. EQ-5D and SF-6D were used for measuring health utility scores of the participants. The consistency of the two instruments was assessed using Bland-Altman plot and Intraclass correlation coefficient (ICC) . Logistic regression models were established to identify predictors of health utility. RESULTS: The participants had a mean utility score of 0.78 (95% confidence interval:0.76, 0.80) in EQ-5D,compared with 0.74 (95% confidence interval: 0.73, 0.76) in SF-6D,and a median (interquartile range) of 0.86 (0.68, 1.00) in EQ-5D and 0.73 (0.62, 0.86) in SF-6D. The 95% limits of agreement between the two instruments ranged from -0.28 to 0.35,with an ICC of 0.67 (95% confidence interval: 0.62,0.71). EQ-5D had a higher ceiling effect. The health utility score of stroke patients changed there rapidly in acute phase (less than 3 months) but barely changed there after.Severity of stroke was a major predictor of health utility scores. CONCLUSION: The two instruments generate inconsistent results in health utility. SF-6D is better for measuring health utility in patients with stroke in China.