Which one of the following investigations is most sensitive for early diagnosis of diabetic nephropathy-

The earliest change in diabetic nephropathy is microalbuminuria which coincides with the pathological changes which include thickening of the glomerular basement membrane and accumulation of matrix material in the mesangium. Thus microalbuminuria is most sensitive investigation for early diagnosis of diabetic nephropathy.Microalbuminuria is defined as 30-299 mg/d of albumin in a 24-h urine collection. It is a good predictor of progression to nephropathy in Type 1 DM. It is less reliable predictor in elderly with Type 2 DM as it may be secondary to factors unrelated to DM, such as hypeension, congestive hea failure (CHF), prostate disease, or infection. Reference : page 830-31 Davidson's Principles and practice of Medicine 22nd edition and page 2425 Harrison's Principles of Internal Medicine 19th edition