TyG in insulin resistance prediction.

Dear Editor,

We read with interest the article “The TyG index cutoff point and its association with body adiposity and lifestyle in children” by Vieira-Ribeiro et al., published in the Jornal de Pediatria, which proposes TyG (triglyceride-glucose índex) cutoff points for the prediction of insulin resistance (IR) in school-aged children and preschoolers. The study makes an important contribution to the topic, considering the need to establish cutoff points to use this tool in the Brazilian pediatric population.

From this perspective, we believe it is very important to warn the authors about a probable mistake in the calculation of TyG. Although the calculation error does not impair the predictive capacity of this method, the proposed cutoff points are significantly altered. This method was proposed by Guerrero-Romero in an article published in 2010, and the calculation is described as follows: [ln(fasting triglycerides) (mg/dL) × fasting glucose (mg/dL)/2], and the values found by the authors was 3.7 (values for healthy adults). However, in another publication by the same authors in 2016, we can verify that the indicated calculation is as follows:[ln(fasting triglycerides (mg/dL) × fasting glucose (mg/dL)]/2, and the values shown by the authors in this article was 4.5 (values for healthy adult men and women).

The chart below shows that, according to the formula used, different TyG values will be obtained, since the first formula divides by 2 before performing the logarithmic operation and the second formula divides by 2 after the logarithmic operation of the serum triglyceride and glucose product.

Therefore, it is likely that the formula used by the authors who proposed the method is the latter of the two, since the values presented in both articles are between 3.7 and 4.5.

This error in the formula presentation led other authors,4, 5, 6 including Vieira-Ribeiro et al., to use the first formula to obtain the TyG, achieving much higher values than those shown by the method’s proponents.

Therefore, we suggest to the authors Vieira-Ribeiro et al. that they recalculate the values of TyG based on the second formula, aiming to present more appropriate cutoffs to the original proposal and to allow an appropriate comparison with future studies, which also must adhere to the proper calculation of this index.

Conflicts of interest

The authors declare no conflicts of interest.

Formula	TG	Glucose	TyG
1st [ln(fasting triglycerides) (mg/dL) × fasting glucose (mg/dL)/2]	168.3	88.3	8.91
2nd [ln(fasting triglycerides (mg/dL) × fasting glucose (mg/dL)]/2	168.3	88.3	4.80