Statistical analysis
Data obtained from the study were entered into an SPSS spreadsheet (version 16) for statistical description and analysis. Categorical variables were presented as percentages and numbers, while quantitative data were expressed as range, standard deviation, mean, median and inter-quartile range. For comparisons of proportions, either the Yates correction, Chi-square test, or Fisher's exact test was employed based on the statistical assumptions that justified each analysis. The level of significance was set at p≤0.05.