Heterogeneity in patterns of progression of chronic kidney disease

Background: Progression of kidney disease is a deceptively simple word for a complex bio-clinical process, evidenced by the number of definitions in the literature. This has led to confusion and differences in interpretation of studies. Methods: We describe different patterns of progression, the performance of different definitions of progression and factors associated with chronic kidney disease (CKD) progression in a public renal service in Australia, in a study of patients enrolled in the CKD.QLD Registry with a minimum of 2 years' follow up. Results: Nine patterns of changing estimated glomerular filtration rate (eGFR) over two consecutive 12-month periods were identified. Most common was a stable eGFR over 2 years (30%), and the least was a sustainable improvement of eGFR over both periods (2.1%). There was a lack of congruence between the several definitions of progression of CKD evaluated. More people progressed using the definition of decline of eGFR of >5 mL/min/1.73 m/year (year 1 = 30.2%, year 2 = 20.7%) and the least using development of end-stage renal disease (year 1 = 5.4%, year 2 = 9.9%). Age (40–59, ≥80 years), degree of proteinuria at baseline (nephrotic range) and CKD aetiology (renal vascular disease, diabetic nephropathy) were significantly associated with eGFR decline over 2 years. Conclusions: This is one of the first demonstrations of the great variations among and within individuals in the progression of CKD over even a period as short as 2 years. Findings suggest considerable potential for renal function recovery and stability while demonstrating the importance of using identical definitions for comparisons across datasets from different sources.