Objective: Clinically, it may be appropriate to subdivide patients with stage 3 chronic kidney disease (CKD) into two subgroups, as they show different risks for kidney outcomes. This study evaluated the proportion of patients with stage 3 CKD who progressed to stage 4 or 5 CKD over 10 years and independent predictors of progression of renal dysfunction. It sought to validate whether stage 3 CKD patients should be subdivided.
Material and methods: This retrospective cohort study enrolled 347 stage 3 CKD patients between January 1997 and December 1999, who were followed up through June 2010. The baseline clinical characteristics and outcomes were compared in patients with stage 3A [45 <estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2)] and stage 3B (30 < eGFR <45 ml/min/1.73 m(2)) CKD.
Results: Of the 347 patients, 196 (58.2%) were in stage 3A. The only difference in baseline characteristics between stages 3A and 3B patients was the degree of albuminuria. During follow-up, 167 patients (48.1%) did not progress, 60 (17.3%) progressed to stage 4 and 120 (34.6%) progressed to stage 5, with 91 (26.2%) starting dialysis. Multivariate Cox regression analysis showed that macroalbuminuria [(hazard ratio (HR) 3.06, 95% confidence interval (CI) 1.48-2.89, p < 0.001], microalbuminuria (HR 1.99 95% CI 1.04-3.85, p = 0.038), microscopic haematuria (HR 2.07 95% CI 1.48-2.89, p < 0.001) and stage 3B CKD (HR 2.99 95% CI 2.19-4.10, p < 0.001) were independent predictors of progression of renal dysfunction. Stage 3B patients had higher risks of adverse renal and cardiovascular outcomes than stage 3A patients.
Conclusions: About half of the patients with stage 3 CKD progressed to stage 4 or 5, as assessed by eGFR, over 10 years. Degree of albuminuria, stage 3 subgroup and microscopic haematuria were important risk factors for progression of stage 3 CKD. It would be appropriate to divide the present stage 3 CKD into two subgroups.