Statistical analyses:
All statistical analyses were performed by IBM SPSS statistics 21.0 (IBM
Corp. Armonk, NY, USA), R Statistical software (version 4.0.3; R
Foundation for Statistical Computing, Vienna, Austria), and GraphPad
PRISM5 software (GraphPad Software Inc, San Diego, CA, USA). Fisher’s
exact test and Pearson’s chi-square test were used for individual
parameter analysis. For testing the association between polymorphism and
outcomes, we used Firth logistic regression that uses a penalized
likelihood to remove much of the bias from the maximum likelihood
estimates in the logistic regression model 28. This
method is best suited for the present study as the genetic variants
tested are rare. Log Rank Mantel-Cox regression analysis was used for
the survival analysis.