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The misidentification of cell lines has been a problem in biomedical research for decades. First noted for HeLa cells, cell lines get mixed up or contaminated with other cells. As a result, researchers publish results based on other cells than they assume. Sometimes this does not affect research results, sometimes it fundamentally flaws the findings. Important efforts have been made to prevent these problems, such as journals requiring genetic verification of cell cultures prior to publication.

But what about the research of the past? We used the ICLAC database of cell lines known to be misidentified to estimate the number of articles in Web of Science using misidentified cells. We found 33.000 publications, currently about 1.200 per year, with no signs of improvement. The articles in this ‘primary contamination’ are in turn cited by 500.000 papers, constituting a ‘secondary contamination’ of the scientific literature.

We suggest publications that base results on misidentified cells should get a warning label, allowing the expert reader to assess the consequences for validity.

Horbach, S., & Halffman, W. (2017). The Ghosts of HeLa: How cell line misidentification contaminates the scientific literature. PLOS ONE. doi:10.1371/journal.pone.0186281.
(12 October 2017, open access)

Here is the media attention.