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Surrogate markers for time-varying treatments and outcomes.

ABSTRACT: BACKGROUND:A surrogate marker is a variable commonly used in clinical trials to guide treatment decisions when the outcome of ultimate interest is not available. A good surrogate marker is one where the treatment effect on the surrogate is a strong predictor of the effect of treatment on the outcome. We review the situation when there is one treatment delivered at baseline, one surrogate measured at one later time point, and one ultimate outcome of interest and discuss new issues arising when variables are time-varying. METHODS:Most of the literature on surrogate markers has only considered simple settings with one treatment, one surrogate, and one outcome of interest at a fixed time point. However, more complicated time-varying settings are common in practice. In this article, we describe the unique challenges in two settings, time-varying treatments and time-varying surrogates, while relating the ideas back to the causal-effects and causal-association paradigms. CONCLUSION:In addition to discussing and extending popular notions of surrogacy to time-varying settings, we give examples illustrating that one can be misled by not taking into account time-varying information about the surrogate or treatment. We hope this article has provided some motivation for future work on estimation and inference in such settings.

SUBMITTER: Hsu JY

PROVIDER: S-EPMC4506229 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Surrogate markers for time-varying treatments and outcomes.

Hsu Jesse Y JY Kennedy Edward H EH Roy Jason A JA Stephens-Shields Alisa J AJ Small Dylan S DS Joffe Marshall M MM

Clinical trials (London, England) 20150506 4

<h4>Background</h4>A surrogate marker is a variable commonly used in clinical trials to guide treatment decisions when the outcome of ultimate interest is not available. A good surrogate marker is one where the treatment effect on the surrogate is a strong predictor of the effect of treatment on the outcome. We review the situation when there is one treatment delivered at baseline, one surrogate measured at one later time point, and one ultimate outcome of interest and discuss new issues arising ...[more]

PMID: 25948621

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Project description:BackgroundThe optimal timing of pars plana vitrectomy (PPV) following ocular trauma is an ongoing debate. Early vitrectomy post-trauma enables the rapid assessment of retinal disease by removing the scaffold that fosters proliferative vitreoretinopathy. On the other hand, late vitrectomy is less challenging as there is a lower risk of bleeding and posterior vitreous detachment induction is easier. The purpose of this work is to report the functional and anatomical outcomes following ocular traumatic injuries in a United States-based cohort, emphasizing the time of intervention.MethodsThis was a retrospective case series of 110 patients with traumatic ocular injuries who underwent PPV between 2008 to 2020. Patients were grouped into four timing categories: same day (0 days), early (1-7 days), delayed (8-14 days), and late (> 14 days). Multivariable regression models controlling for confounding were implemented to assess the impact of vitrectomy timing on anatomical and functional outcomes. Visual acuity (VA) at baseline and after surgery, proliferative vitreoretinopathy (PVR), and enucleation for each vitrectomy timing category were recorded.ResultsPatient demographics and severity of ocular trauma were comparable across timing categories. Final VA in LogMAR was found to have a stepwise worsening as the time of ocular trauma to vitrectomy was increased (p < 0.05). For every one-step increase in the vitrectomy timing category, there was an adjusted 0.24 (CI 0.04-0.44) increase in final VA. No patient in the same day vitrectomy group had an enucleation or PVR, while patients who had late vitrectomies had the largest number of both enucleations and PVR (44.4% and 52.0%, respectively). In adjusted analysis, there was 3.11 increased odds (CI 1.03-9.42) of developing PVR for a one-step increase in vitrectomy timing (p < 0.05).ConclusionVitrectomy on the same day of injury has the best final VA, and the lowest incidence rates of PVR and enucleation in comparison to other timing categories, regardless of etiology.

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Surrogate markers for time-varying treatments and outcomes.

Publications

Surrogate markers for time-varying treatments and outcomes.

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