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Cochrane withdraws review on zinc for colds for data concerns

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Cochrane_LogoThe Cochrane Library has withdrawn a 2013 systematic review on zinc’s ability to fight the common cold.

Cochrane often marks reviews “withdrawn” once new evidence emerges that renders them out of date — but in this case, the review was flagged while the editors investigate issues “regarding the calculation and analysis of data.”

Here’s the notice.

This review was withdrawn due to concerns raised via the feedback mechanism regarding the calculation and analysis of data in the review in April 2015. Whilst it is not unusual for reviews to be withdrawn, the editorial group took the view that it would be better to take a cautious approach and explore the source and calculation of data used in the analysis in more detail, rather than keep the review on the Cochrane Database of Systematic Reviews for the time being. To view the published versions of this article, please click the ‘Other versions’ tab.

The latest version of “Zinc for the common cold” was published in 2013 by a pair of researchers based in India, Rashmi Das and Meenu Singh, who also authored the 2011 version of the review. It has been cited five times, according to Thomson Scientific’s Web of Knowledge.

Singh confirmed to us that one of the “concerns” that triggered the inquiry stems from Harri Hemilä, a public health researcher at the University of Helsinki.

Hemilä authored a 2011 review in The Open Respiratory Medicine Journal, “Zinc Lozenges May Shorten the Duration of Colds: A Systematic Review.” In an emailed statement to us, he said he submitted comments on the 2011 review, but spotted some of the same “errors” in the 2013 version:

The Cochrane review (2011) had errors and the above PubMed Commons comments summarize them.

However, I wrote a much more detailed criticism which was published as part of the Cochrane review under the feedback classification within the review.

Hemilä told us that Singh and Das, the authors of the Cochrane review,

…did not properly respond to my comments nor correct their review on the basis of my 2011 comments.

Thus, most of the 2011 errors remained in the updated 2013 review.

Furthermore, the 2013 update had copied parts of my 2011 paper as ideas, as data and as sentences without attributing my 2011 paper.

Last winter, Hemilä wrote an analysis of the 2013 Cochrane update, and in February he posted the analysis at his university’s repository:

I sent the Cochrane Acute Respiratory Infection group a summary of my concerns and the link and asked them to look at the case.

They passed the problem to the main editorial group of the Cochrane Collaboration.

Hemilä was not aware of the withdrawal before we contacted him. He noted that the same authors wrote a JAMA evidence synopsis based on the 2013 review, in which he “found a number of problems.” He submitted a report on that to his university repository, too.

Singh and Das issued a response addressing Hemilä’s comments on August 18.

Hemilä also listed many of his concerns in 2014 posts on PubMed Commons and PubPeer detailing “errors in the extraction of data” and “numerous methodological problems.”

When reached by email, Das said that the review was only withdrawn “temporarily:”

The issues raised were addressed and they are being examined by the Cochrane review group, so the review is withdrawn temporarily. Please wait till the things get clearer.

Singh gave a similarly brief statement:

The issues raised were addressed. The comments are being examined by review group, so the review is withdrawn for the time being which is common for Cochrane reviews since they are regularly updated, this review is also under revision.

A spokesperson for Cochrane declined to comment on a pending investigation.

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