Statistical Analysis
Statistical analysis was performed using SPSS BASE 17.0 statistical software (SPSS Inc. Chicago, IL, USA). Categorical variables were expressed as percentages and compared using the Chi-square or Fisher’s exact test, as appropriate (n ⩽ 5 per group). Continuous variables were expressed as mean ± 1 standard deviation and were compared using the Student’s t test. A two-tailed p-value less than 0.05 was taken to indicate statistical significance.