Data were analyzed by way of χ2 tests and multivariable regression analysis.

Differences between groups were estimated using the χ2 test or Student's t-test

In the case of DNA, the χOL4 correction gives only partial improvement.

Risk factors were evaluated using χ2 and Wilcoxon tests and multivariable logistic regression.

Statistical analysis included χ2 tests and Cox proportional hazards regression analysis.