Medical care costs associated with progression of diabetic nephropathy

To estimate the direct medical costs of hypertensive patients with type 2 diabetes by the level of proteinuria and to evaluate the differences between patients whose nephropathy did and did not progress.

We identified 7,758 patients with diabetes and hypertension who had a urine albumin-to-creatinine ratio (UACR) during 2001-2003 and at least one follow-up UACR 3-5 years later. Patients were followed for up to 8 years for progression of nephropathy, which was defined by increasing levels of proteinuria: normoalbuminuria (UACR < 30 mg/g), microalbuminuria (30-299 mg/g), macroalbuminuria (≥300 mg/g), and end-stage renal disease (dialysis or transplant). We calculated annualized inpatient, outpatient, pharmaceutical, and total medical costs incurred by patients after the baseline measure through 2008, comparing patients who did and did not progress to a higher nephropathy stage. We also compared pre- and postprogression costs among those whose nephropathy progressed.

Patients with normoalbuminuria who progressed to microalbuminuria experienced an annualized change in baseline costs that was $396 higher (P < 0.001) than those who maintained normal albuminuria ($902 vs. $506). Among those with microalbuminuria, progression was significantly associated with a $747 difference (P < 0.001) in annualized change in outpatient costs compared with no progression ($1,056 vs. $309). Among patients who progressed, costs were 37% higher following progression from normoalbuminuria to microalbuminuria ($10,188 vs. $7,424; P < 0.001), and 41% higher following progression from microalbuminuria to macroalbuminuria ($12,371 vs. $8,753; P < 0.001).

Progression of nephropathy was strongly associated with higher subsequent medical care costs in hypertensive patients with diabetes. Greater prevention efforts may reduce the substantial economic burden of diabetic nephropathy.