In a recent analysis of thousands of randomized controlled trials (RCT) in eight journals a simple method was offered which might enable skeptical scientist identification of data fabrication. Editor of the Anaesthesia journal John B. Carlisle of Torbay Hospital, UK, looked at baseline differences of means in more than 5000 randomized controlled trials, mainly in the field of Anesthesiology, but also more than 500 published in JAMA and more than 900 published in the New England Journal of Medicine . His study went online earlier this week. Analyzed articles were published between 2000 and 2015. In brief, if randomization was successful, baseline differences should be small. Giving p-values for baseline differences (in order to indicate successful randomization) is actually discouraged since they are not really interpretable, but Carlisle calculated them anyway. If the null hypothesis is true, p-values have a uniform distribution. So p-values between 0 and 1 would be equally likely.
The November 2012 EFP and AAP workshop on systemic health and how it is affected by periodontal disease has resulted in the joint publication of a couple of valuable systematic reviews in both Journal of Clinical Periodontology and Journal of Periodontology. I have expressed my strong opinion here on this blog that, in essence, there was not so much new or surprising. That there is strong evidence for minor effects of periodontitis on, say, cardiovascular disease and that diabetes mellitus is affected by periodontal disease while it is a risk factor for gum disease itself has been known for decades. That, what organizers had claimed, there is now a need for intervention studies to show that the risk for cardiovascular events may be reduced, has been questioned on this blog and elsewhere.
I have criticized the workshop’s Manifesto, a press release which reduced the somewhat difficult to digest information to a message for the public (and I include here in particular most of the dental profession whose members may not be able or willing to read through the pages of documents, be it but systematic reviews let alone the original cohort studies). I have also suggested a brief example (based on a gut feeling of a possible risk ratio) in which the most relevant ethical problem of not treating huge cohorts for periodontal disease was mentioned while probably a great number of patients with periodontitis had to be treated successfully (number needed to treat) in order to prevent a single cardiovascular event (if the effect was causal) which renders the whole exercise probably irrelevant.