Statistical analysis
Categorical data were compared with the χ2 or Fisher’s exact test, as appropriate, and results are reported as absolute and relative frequencies. Quantitative variables with a normal distribution were compared witht tests and results are reported as the mean and standard deviation (SD), while variables with a skewed distribution were compared with the nonparametric Mann-Whitney U test and results are expressed as the median and interquartile range (IQR). The threshold for significance was set at P <0.05 (all tests 2-tailed). All analyses were performed with GraphPad Prism v8 (GraphPad Software, San Diego, CA).