Corrected Report of PREDIMED Trial

You are being asked to read this study because 

it is a corrected report, the study results were originally published in 2013 and received significant media attention. However, in 2017, it became clear that the original randomization plan had been jeopardized: 

"....Our original report was published in the Journal  in 2013.10  A 2017 analysis11 of the distributions of baseline variables in randomized trials identified the PREDIMED trial as having distributions that were significantly different from what would have been expected to result from randomization. This report led to our conducting a review of how participants were assigned to various intervention groups; that review revealed irregularities in our randomization procedures. Therefore, we have withdrawn our original report12 and now publish a new report...."

So, the goal in asking you to read the 2018 study is not to ask you to identify the things that were done incorrectly, but to see how the investigators were able to re-evaluate their data to present corrected findings.  In order to do this, you will also need to read the following PREDIMED intervention profile paper that describes the original methods: 

(a) What were the original eligibility criteria for participants in recruited into this study as described in the 2012 methods paper?

(b) On page 34 (3) of the 2018 paper, the authors provide information on 425 additional participants. Why was it important to note this additional recruitment information?

(a) How was randomization originally conducted as described in the 2012 methods paper? 

(b) In the 2018 paper, what update do Estruch and colleagues provide on the randomization schemes employed across sites?

(a) What was the intervention tested in this trial?

(b) What was the control condition? 

(c) How could this control condition influence the study results? 

(d) How was adherence to each of the intervention arms assessed?

(a) What was the primary endpoint?

(b) What were the secondary endpoints?

(c) How were endpoints ascertained?

The following questions are based on findings presented in Table 2 of the 2018 report:

(a) What do the data presented in this table suggest?

(b) Why is it important to compare baseline characteristics of participants across trial arms?

The following questions are based on the findings presented in Table 3 in the 2018 paper:

(a) What can you say about the incidence rate for the primary endpoint across the intervention arms?

(b) Calculate the basic incidence density ratio comparing:

- mediterranean diet with EVOO to control condition

- mediterranean diet with nuts to control condition

(c) Interpret what the incidence density ratios calculated in (b) mean:

- mediterranean diet with EVOO to control condition

- mediterranean diet with nuts to control condition