'Microalbuminuria' and diabetes: a critique--assessment of urinary albumin excretion and its role in screening for diabetic nephropathy.

Abnormal albumin excretion in the range not previously detectable by routine clinical methods can now be readily quantified, and has been shown to predict the development of clinically significant nephropathy in insulin-dependent diabetes mellitus (IDDM) and to predict excess mortality in non-insulin-dependent diabetes mellitus (NIDDM). Albuminuria of this degree has been inappropriately called "microalbuminuria," a misleading term which should be abandoned. In IDDM, persistent minimal elevation of albumin excretion predicts the development of more severe proteinuria and clinical diabetic nephropathy, which frequently progresses to renal failure. In NIDDM, the predictive value for renal failure remains to be established, but excess mortality occurs in those with abnormal albumin excretion, suggesting that it is an indicator of generalized vascular disease. However, the normal range of albumin excretion in older subjects is not well established. The relationship of glomerular injury to mildly elevated albumin excretion is uncertain. Several means of reducing the excretion rate have been described, but whether these can halt or prevent progression of glomerular injury is unknown. Thus, at the present time detection of mildly elevated albumin excretion and intervention to reduce the incidence of diabetic nephropathy or other diabetes-related complications fail to meet generally accepted criteria for prescriptive screening. However, such measurements of albumin excretion provide an important tool for research into the natural history and pathogenesis of diabetic nephropathy.