Statistical methods
SECONDARY
Analyses were conducted at the level of the individual filter, in both an intention-to-treat and per-protocol fashion. Continuous variables are reported as means and standard deviations or as medians and interquartile ranges; categorical variables are reported as frequencies and proportions. The primary analysis compared the average filter life in the pre-filter CVVH and CVVHD groups in an intention-to-treat fashion. Because the distribution of filter life was not normal, and filters are nested within patients, generalized linear mixed models (GLMM) with gamma distribution was used with a log link function and a random intercept. Because of the wide latitude given to providers, there were limited instances where the modality was changed during the course of CKRT. Primarily, this resulted in a change to CVVHDF with a combination of pre-filter and dialysate fluid. A secondary analysis compared filters in the pre-filter CVVH and CVVHD groups based on actual modality delivered after removal of CVVHDF filters. A filter survival curve was generated for filter time in the primary analysis. All statistical tests were considered to be significant at a 2-sided p < 0.05. All analyses were performed using SAS software version 9.4 (SAS Inc., Cary, NC).