From the Guidelines
Microalbuminuria is a significant predictor of diabetic nephropathy and cardiovascular disease (CVD) risk in patients with Diabetes Mellitus (DM).
Significance of Microalbuminuria
- Microalbuminuria, defined as an albumin excretion rate of 30-299 mg/24 h, is the earliest stage of diabetic nephropathy in type 1 diabetes and a marker for development of nephropathy in type 2 diabetes 1.
- It is also a well-established marker of increased CVD risk, with a continuous relationship between cardiovascular and non-cardiovascular mortality and urinary protein/creatinine ratios 1.
Screening and Diagnosis
- Screening for microalbuminuria can be performed by measuring the albumin-to-creatinine ratio in a random, spot collection, which is the preferred method 1.
- At least two of three tests measured within a 6-month period should show elevated levels before a patient is designated as having microalbuminuria 1.
Treatment and Prevention
- Intensive diabetes management with the goal of achieving near normoglycemia has been shown to delay the onset of microalbuminuria and the progression of micro- to macroalbuminuria in patients with type 1 and type 2 diabetes 1.
- ACE inhibitors or angiotensin II receptor antagonists are recommended for patients with microalbuminuria and proteinuria, regardless of baseline blood pressure 1.
- Dietary factors, such as energy and sodium restriction, and supplementation with vitamin C and vitamin E, may also play a role in preventing nephropathy 1.
From the Research
Definition and Significance of Microalbuminuria
- Microalbuminuria is defined as the persistent elevation of albumin in the urine, with values ranging from 30-300 mg/day (20-200 microg/min) 2.
- It is an established risk factor for renal disease progression in type 1 diabetes and is considered the earliest clinical sign of diabetic nephropathy 2, 3.
- Microalbuminuria is also an important risk factor for cardiovascular disease and defines a group at high risk for early cardiovascular mortality in both type 2 diabetes and essential hypertension 2, 4.
Prevalence and Risk Factors
- The prevalence of microalbuminuria in type 2 diabetes mellitus (T2DM) patients is significantly high, with a reported prevalence of 39.1% 5.
- Risk factors associated with microalbuminuria include hypertension, male gender, suboptimal control of diabetes mellitus, high HbA1c levels, longer disease duration, dyslipidemia, and other diabetic complications such as neuropathy and retinopathy 5.
- There is a statistically significant correlation between microalbuminuria and hypertension, diabetes duration, HbA1c level, dyslipidemia, and therapy type 5.
Mechanism and Pathophysiology
- Microalbuminuria arises from the increased passage of albumin through the glomerular filtration barrier, requiring ultrastructural changes rather than alterations in glomerular pressure or filtration rate alone 6.
- The loss of systemic endothelial glycocalyx in diabetes suggests that damage to this layer represents a missing link in the development of microalbuminuria 6.
- Glomerular endothelial dysfunction, and in particular damage to its glycocalyx, represents the most likely initiating step in diabetic microalbuminuria 6.
Screening and Management
- The use of the albumin-to-creatinine ratio is recommended as the preferred screening strategy for all diabetic patients 2.
- Microalbuminuria should be checked annually in everyone, and every 6 months within the first year of treatment to assess the impact in patients started on antihypertensive therapy 2.
- Aggressive blood pressure reduction, using antihypertensive agents such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and beta blockers, can reduce microalbuminuria and prevent progression to overt proteinuria 2, 3.