Table 2.

Predictors of baseline urine creatinine and rate of change of urine creatinine over time in years (linear mixed model)

PredictorsAverage Difference on UCr95% Confidence Intervals
Variables associated with baseline UCr (mg/d)
 Intercepta (CKD stage 3a)1025985 to 1065
 CKD stage 3b versus CKD stage 3a−16−55 to 24
 CKD stage 4 versus CKD stage 3a−34−73 to 5
 CKD stage 5 versus CKD stage 3a−105−158 to −52
 Men (versus women)281253 to 308
 Diabetes (present versus absent)−34−71 to 1.6
 Age (10 yr)−63−72 to −54
 Protein intake (10 g/24 h)8178 to 85
 BMI (10 kg/m2)6239 to 84
Variables associated with the rate of change of UCr (mg/d per year)
 Time (yearly change in CKD stage 3a to 4)−16−19 to −14
 Time (yearly change in CKD stage 5)1.4−10 to 13
  • UCr, 24-hour urinary creatinine; BMI, body mass index.

  • a The model intercept estimates the mean UCr excretion for a 57-year-old nondiabetic woman with CKD stage 3a (reference category), a BMI of 26.5 kg/m2, and a protein intake of 65.6 g/d (mean values of continuous covariates included in the models). Average effects on UCr are the regression coefficients or average effects on the baseline excretion rate in milligrams per day (the model intercept) and the rate of change of UCr in milligrams per day per year (the model slope) associated with the covariates in the model. The slope was not affected by age, BMI, current values of estimated GFR, or individual estimated GFR intercept and slope (estimated using linear mixed models). Results of sensitivity analysis are reported in Supplemental Material (Supplemental Table 2).