Statistical analysis
Descriptive statistics: Continuous data is presented as median with
interquartile ranges (IQR; 25 - 75). For comparisons of quantitative
variables between 2 groups, the Mann-Whitney U test was used, while the
Kruskal-Wallis test followed by Dunn’s test was used to compare ≥3
groups. Categorical values are presented as number and percentage.
Chi-squared test was used to compare categorical variables between
groups. The statistical analysis was performed using the SPSS software
v.21.0 (IBM). P value ≤ 0.05 was considered significant.
The study was approved by the Institutional Review Board of the
Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán
(Ref. 2232). All subjects gave their informed consent to participate
according to the Declaration of Helsinki.