Sequence of progression of albuminuria and decreased GFR in persons with type 1 diabetes: a cohort study.

BACKGROUND: The sensitivity of albuminuria in predicting loss of kidney function has been questioned. We determined the sequence of kidney disease stages (microalbuminuria, macroalbuminuria, low estimated glomerular filtration rate [eGFR], and end-stage renal disease [ESRD]) and characterized those without albuminuria before a low eGFR.

STUDY DESIGN: The Pittsburgh Epidemiology of Diabetes Complications Study is a prospective cohort investigation of childhood-onset type 1 diabetes.

SETTING & PARTICIPANTS: 480 study participants with eGFR greater than 60 mL/min/1.73 m(2) (mean age, 27 years; diabetes duration, 19 years at study entry) were prospectively followed up for 16 years.

OUTCOMES & MEASUREMENTS: Low eGFR was defined as creatinine clearance less than 60 mL/min/1.73 m(2) from timed urine collections; microalbuminuria, as albumin excretion rate between 20 to 200 microg/min (30 to 300 mg/24 h); macroalbuminuria, as albumin excretion rate greater than 200 microg/min (>300 mg/24 h); and ESRD, as dialysis or renal transplantation.

RESULTS: The 33 of 480 individuals (7%) who developed ESRD had prior albuminuria. 71 of 480 (15%) individuals developed low eGFR. 66 of 71 (93%) had prior/concurrent albuminuria, and 5 of 71 (7%) did not. Incident low eGFR values in the 5 patients were: (1) 54, (2) 58, (3) 59, (4) 59.7, and (5) 59.8 mL/min/1.73 m(2). 3 of 5 (60%; patients 1, 4, and 5) subsequently developed albuminuria. Final eGFRs in the 5 patients were: (1) 94, (2) 86, (3) 60, (4) 65, and (5) 54 mL/min/1.73 m(2), respectively.

LIMITATIONS: GFR and insulin sensitivity were not measured, but estimated. Incident decreased eGFR in patients without preceding/concurrent albuminuria may be caused by misclassification or a temporary eGFR decrease.

CONCLUSIONS: Moderately decreased eGFR may occur rarely in patients with type 1 diabetes without preceding albuminuria.