Microalbuminuria in Type 2 Diabetes and Hypertension
A marker, treatment target, or innocent bystander?
Seema Basi, Pierre Fesler, Albert Mimran, Julia B. Lewis


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 in albumin excretion, it is subject to collection errors. The Kidney Disease Outcomes Quality Initiative guidelines state that ACR measurement in a first-morning spot urine collection is adequate and a timed urine collection is not necessary (14). However, because women excrete less creatinine than men and microalbuminuria is based on a fixed amount of urinary albumin excretion per day, the definitions of microalbuminuria are different in men and women when using ACRs (15).

Comments: (0)