Hi there! I'm trying to do a surrogate endpoint validation on aggregated data (trial level). What I have is a bunch (N ~ 50) of studies reporting an estimate (hazard ratio [CI95%]) for the "true" endpoint (overall survival) and another estimate for the surrogate endpoint (progression-free survival). My aim is to compute the surrogate threshold effect, that is the minimum amount of PFS effect able to predict a non-zero (significant) effect on OS. I'd like to do that in accordance with this publication, which says: we fitted a random effects mixed-model to the data with moderator HRPFS and outcome variable hazard ratio of OS (HROS) weighted by standard error (SE) of OS using the restricted maximum likelihood (REML) estimator for the amount of heterogeneity. [...] Based on the regression fit, we calculated a prediction band to a significance level of α = 0.05 for HROS. Meta-regression model and prediction values were implemented with R [16] using functions rma.uni and predict.rma from metafor package [17]. The STE resulted from the intersection of the upper prediction limit curve and the horizontal where HROS = 1 (zero effect). In SAS PROC MIXED, do I have the opportunity do plot 95% prediction bands from which I could obtain the STE? If yes, could you give me a sample code? Thank you very much in advance!
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