Statistical analysis
All statistical analyses were fulfilled using IBM SPSS Statistics software (Version 24) (IBM SPSS Statistics, Armonk, USA). The normality of variables was established using the Kolmogorov- Smirnov test. To compare variables with non-normal distribution, Mann–Whitney U test was employed. The predictive value of serum D-dimer level was determined via measuring the Area Under Receiver Operating Characteristic (AUROC) curve. Finally, the optimal threshold value was obtained via the calculation of Youden index. A p-value of less than 0.05 was regarded to be statistically significant.