EXPRESSION OF CONCERN: Prioritising primary care patients with unexpected weight loss for cancer investigation: diagnostic accuracy study

BMJ alerts readers to a problem with the content of this paper by Nicholson and colleagues (BMJ 2020;370:m2651, doi:10.1136/bmj.m2651, published 13 August 2020). The authors of the paper recently identified an error in their approach to the research. Some patients were excluded from the study because their healthcare records contained a code that was not associated with weight loss. Sometime later, however, some of these patients are likely to have had a code included in their healthcare record that was associated with unintended weight loss and cancer. This created an unintended selection bias in the work; some patients were excluded from the study who should have been included in the study. Rectifying this error would result in substantially more patients being included in the study. Reanalysis changes the study’s key results and messages. It corrects an underestimate of the likelihood of cancer for some men, and a larger group of women. BMJ is working with the authors to review a new version of the paper and to determine what post-publication action is suitable in this case. An update will be provided when our evaluation has concluded.