Discordant results about QT prolongation in patients with Turner syndrome.

To the Editor,

We have read the paper entitled “Evaluation of the Tp-Te interval, Tp-Te/QTc ratio, and QT dispersion in patients with Turner syndrome’’ with great interest (1). The authors stated that patients with Turner syndrome have a longer QTc; however, the numbers of patients in the control group were insufficient. The control group in the study included 35 patients, and the mean QTc was 392.06±13.21. In previous studies with a larger population, the mean QTc of patients was longer than that in the present study. For example, in the previous studies for ages 12–15 years, the mean QTc was 426 for 10,709 female population, whereas for ages 16–19 years, the mean QTc was 423 for 14,453 female population in the large study (2). This raises suspicion about selection bias in the control group. Furthermore, the selection of an inappropriate control group is a common problem in this type of observational study. Inappropriate control group can result in inconsistency with real population statistics. In addition, even if we accept that an accurate control group was selected by the authors, the effect of a small increase in QTc on mortality rate is unclear. We cannot exclude the chance factor for statistical significance (p value) because of the small sample size and small number of patients in the control group of the authors’ study. Moreover, in the discussion part, there is not enough data and causality for the prevention of sudden death in patients with Turner syndrome.