tokens: Multivariate stepwise logistic regression analysis using preoperative and postoperative variables identified that an increase of serum creatinine compared with average at 1 year , 3 months , and 4 weeks postoperatively were independent risk factors for the development of CRF or ESRD with odds ratios of 2 . 6 , 2 . 2 , and 1 . 6 , respectively .