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Long‐term effect of first‐line injectable multiple sclerosis treatments: input of a time‐dependent propensity score

Abstract : Purpose: The long-term effect of beta-interferon and glatiramer acetate on multiple sclerosis (MS) disability progression has resulted in controversial results, probably due to a lack of appropriate control of biases as raised in observational studies. In particular, the time of the therapeutic decision is difficult to define when the controls are not treated. Methods: This retrospective observational study was based on a series of patients from the MS expert center in Rennes, France. We used a time-dependent propensity score defined as the linear predictor of a Cox model estimating the hazard of being treated at each time from MS onset. The matching procedure resulted in two groups: patients matched as treated and as not yet treated. The restricted mean times (RMST) to reach a moderate level of disability or worsening of the disability were compared between the two groups in an intention-to-treat analysis. Results: Of the 2383 patients included in the study, 556 were matched as treated. The matching procedure provided a good balance of both the time-fixed and the time-dependent covariates. A slight difference was observed for the time to reach a moderate level of disability, in favor of the "not yet treated" group (difference in the RMST: -0.62 [-0.91; -0.33]) while no difference was found in terms of worsening of the disability (-0.03 [-0.24; 0.33]). Conclusion: This unexpected result is probably due to unmeasured confounders. However, this time-dependent PS warrants consideration in long-term effectiveness studies.
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https://hal.ehesp.fr/hal-02979802
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Submitted on : Tuesday, October 27, 2020 - 11:55:56 AM
Last modification on : Friday, November 20, 2020 - 3:05:29 AM

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Mathilde Lefort, Yohann Foucher, Remi Lenain, Sandra Vukusic, Gilles Edan, et al.. Long‐term effect of first‐line injectable multiple sclerosis treatments: input of a time‐dependent propensity score. Pharmacoepidemiology and Drug Safety, Wiley, 2020, ⟨10.1002/pds.5154⟩. ⟨hal-02979802⟩

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