Background: The aim of this study was to investigate the annual rate of glomerular filtration rate (GFR) decline and risks for this decline in association with albuminuria progression in type 2 diabetes.
Methods: An observational 4-year cohort study was performed on 1002 subjects with preserved GFR (699 normoalbuminuric), and the predictive value of baseline variables on the GFR slope was investigated. GFR decliner and albuminuria progressor were defined as a GFR slope <-4.0%/year and changes in the geometric mean of urinary albumin from baseline to follow-up >150%, respectively.
Results: Annual rates of GFR decline (percent per year, median and interquartile range) were -2.58 (-4.70 to -0.48) in normoalbuminuria, -3.49 (-5.93 to -1.11) in microalbuminuria and -6.58 (-10.64 to -3.53) in macroalbuminuria. Subjects cross-classified according to GFR decliner/albuminuria progressor consisted of 51% (-/-), 13% (-/+), 28% (+/-) and 8% (+/+). Common risks for GFR decline and albuminuria progression were retinopathy, neuropathy, hemoglobin A(1C) (HbA(1C)) and urinary albumin. Independent significant risks for GFR decline were baseline GFR, systolic blood pressure (SBP), total protein (TP) and hypertension. Proportions with progression to albuminuria were similar between GFR decliners and non-decliners. Multiple linear regression analysis indicated that GFR slope was predicted by baseline variables of urinary albumin, GFR, HbA(1C), SBP, plasma TP and retinopathy. These risks appeared variable according to high or low levels of urinary albumin and GFR.
Conclusions: Urinary albumin excretion is only one risk factor for albuminuria progression and GFR decline, and other important factors were implicated as important for prevention of end-stage renal disease.