Getting it All Wrong

In an announcement for his talk about periodontal treatment effects on type 2 diabetes at Europerio 8 in London later this year, exasperated Professor Thomas Kocher of Greifswald University in Germany promises to “dissect” the large multicenter trial by Engebretson et al. (2013) who could not find an effect on glycated hemoglobin in type 2 diabtes mellitus. The study had been published in late 2013 in JAMA, not in New England (Journal of Medicine). The large multicenter trial  had long been attacked for not yielding the desired results (“a publication which we were really waiting for”).

Kocher was asked to talk in London about “why all the other small studies showed an effect” and he wants to find out “the issues why we [?] couldn’t see anything in the Engebretson study”. Well, it was actually Wenche Borgnakke who had got 20 other “reviewers” aboard who had already dissected the study by Engebretson et al. and has called for censorship.

As noted by Engebretson and Kocher 2013 in one of the numerous previous systematic reviews of RCTs on the effect of nonsurgical periodontal therapy and reported in Table 1 of their article, problems with the design of these small-scale, mainly single-center studies, which included some trials with adjunctive antibiotics, were plentiful. Problems with low and high baseline HbA1c levels and with questionable periodontal outcomes had been reported as well. Engebretson and Kocher (2013) report possible publication bias which means nothing else that studies without an effect on HbA1c might have gone unpublished. Based on this particular and numerous other systematic reviews, the evidence that nonsurgical periodontal therapy in fact has a relevant beneficial effect on HbA1c levels in type 2 diabetics may actually be regarded moderate. The study by Engebretson et al. adds heterogeneity to any meta-analysis which may downgrade this evidence to low. That is what our thought leaders alerts. That’s why censorship.

That the unwelcome results, published in JAMA, are now more and more reduced to principal investigator Steven Engebretson of NYU, New York, is more than regrettable. The study is co-authored by 16 periodontal scientists, including department chairs of 7 or so university dental schools. Anyway, the study does have undeniable problems, but so have most of the RCTs in previous systematic reviews. Most important is probably that participants in the study by Engebretson et al. were not prescribed an antimicrobial mouthwash such as 0.1-0.2% chlorhexidine. Plaque levels (as well as bleeding scores) remained high despite efforts to reinforce oral hygiene after three months. Highly obese participants may further have resulted in no effect of nonsurgical periodontal therapy, and they may or may not represent U.S. American type 2 diabetics. Borgnakke et al. (2014) had criticized that some baseline HbA1c levels were below and above inclusion criteria disregarding the fact that patients had been randomized after enrolment and baseline data had been taken afterwards. Given some fluctuation in HbA1c levels, the intention-to-treat principle demands that once randomized, the subject must not be removed from the trial.

1 March 2015 @ 10:09 am.

Last modified March 1, 2015.


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