Microalbuminuria in Type 2 Diabetes and Hypertension
A marker, treatment target, or innocent bystander?
- Seema Basi, MD, MSCI1,
- Pierre Fesler, MD2,
- Albert Mimran, MD2 and
- Julia B. Lewis, MD3
- 1University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, New Jersey
- 2Department of Internal Medicine, Hôpital Lapeyronie, Montpellier, France
- 3Vanderbilt University Medical Center, Nashville, Tennessee
- Address correspondence and reprint requests to Julia B. Lewis, MD, Vanderbilt University Medical Center, 1161 21st Ave. South and Garland, Division of Nephrology, S-3223 MCN, Nashville, TN 37232-2372. E-mail: julia.lewis{at}vanderbilt.edu
- ACR, albumin-to-creatinine ratio
- AER, albumin excretion rate
- ARB, angiotensin receptor blocker
- GFR, glomerular filtration rate
- IDNT, Irbesartan Diabetic Nephropathy Trial
- LIFE, Losartan Intervention for Endpoint Reduction in Hypertension
- LVH, left ventricular hypertrophy
- PREVEND, Prevention of Renal and Vascular End-Stage Disease
- RENAAL, Reduction of Endpoints in Non-Insulin Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan
- SAP, systolic arterial pressure
Albuminuria is a well-known predictor of poor renal outcomes in patients with type 2 diabetes and in essential hypertension (1–4). Albuminuria has also been shown more recently to be a predictor of cardiovascular outcomes in these populations (5–8). There is emerging data that reduction of albuminuria leads to reduced risk of adverse renal and cardiovascular events (9–12). It has become increasingly clear that albuminuria should not only be measured in all patients with type 2 diabetes and hypertension, but also steps should be taken to suppress albuminuria to prevent future renal and cardiovascular adverse events. This review discusses the measurement of albuminuria and summarizes the current literature on the association between albuminuria and adverse cardiovascular and renal outcomes in type 2 diabetes and hypertension. It also summarizes the evidence that reduction of albuminuria leads to improvement in the risk profiles of these patients.
DEFINITION AND MEASUREMENT OF ALBUMINURIA—
Microalbuminuria is defined as levels of albumin ranging from 30 to 300 mg in a 24-h urine collection (13). Overt albuminuria, macroalbuminuria, or proteinuria is defined as a urinary albumin excretion of ≥300 mg/24 h. Urinary albuminuria comprises 20–70% or urinary total protein excretion. Measuring urinary albumin excretion by dipstick without simultaneously measuring creatinine is subject to false-negative and false-positive results due to variations in urine concentration caused by hydration level (13). Although urinary dipsticks are acceptable for quick screening, other more precise measurements should be done to quantify urinary albumin excretion rates (AERs). Albuminuria can be measured in several ways (Table 1): 1) measurement of albumin-to-creatinine ratio (ACR) in a random or first morning spot collection, 2) 24-h urine collection with measurement of creatinine to verify adequacy of the collection, and 3) timed (4-h or overnight) urine collections (13). Although the 24-h urine collection would overcome issues of diurnal variation …
