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.