The article by Dr Pastor-Villaescusa may make a valuable contribution to the literature if interpreted correctly. However, in its current form, it contains an important error of statistical inference.
Specifically, the abstract states that “Metformin decreased the BMI z score and improved inflammatory and cardiovascular-related obesity parameters in prepubertal children but not in pubertal children. Hence, the differential response according to puberty might be related to the dose of metformin per kilogram of weight.”
Yet, in contrast to the statement above, the body of the article states, “No differences were found in the impact of metformin according to the pubertal stage when the interaction time × treatment × puberty was applied to the entire population (P = .41).” Furthermore, Table 2 shows that the placebo-corrected reductions in BMI z score in the prepubertal and pubertal groups are, within the precision reported in the table, identical.
In short, there is no evidence for a “differential response” by pubertal status, contradicting the authors’ conclusion statement. The authors have made a common but serious error of inference by neglecting the fact that “Difference in Nominal Significance is not a Significant Difference,” as has been described elsewhere.1,2
The conclusion offered by the authors is not supported by the data and should be corrected.
CONFLICT OF INTEREST: The author has indicated he has no potential conflicts of interest to disclose.
- Copyright © 2017 by the American Academy of Pediatrics