Stratified Analyses

To examine for predefined interactions, additional Cox regression analyses were performed in strata defined by (1) PRA peak 0% versus >0% and (2) calcineurin inhibitor (tacrolimus versus cyclosporin). Finally, in the subset of patients insured by Medicare, first transplant nephrectomy was identified using ICD-9-CM Code 55.53 in Medicare claims data, and multivariate Cox proportional hazards models were performed in strata identified by nephrectomy (yes/no) and PRA before second transplant.