Statistical analysis
Continuous variables were described as the mean + SD for normally distributed data and median (25% to 75% quartile) for non-normally distributed data, and comparisons between groups were performed with Student t test. Categorical variables were described as counts and compared by chi-square analysis. Using the pulmonary venography as the gold standard, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated including the 95 % confidence interval (CI) based on a binomial distribution. The receiver operating characteristic (ROC) curve was delineated and area under curve (AUC) was calculated to determine the diagnostic ability of both tools. Spearman correlation was conducted to investigate the relationship between occlusion degree and corresponding cryoablation parameters.
All tests were 2-tailed, and a statistical significance was established at P < 0.05. All analyses were performed using SPSS software (version 22.0; SPSS, Inc., Chicago).