2.5 Analyses
SPSS 24.0 was used to calculate the incidence rates of the clinical characteristics. The percentage of distribution of causes/medical history of each group was expressed by the percentage of ascertained causes/ medical history of each group to the total number of causes/ medical history of each group. The chisquare (X2) test was used to evaluate the variable. Statistical significance was defined as a two-tailed P-value less than 0.05.