Renal function in diabetic nephropathy

Table 1 The various tests for chronic tubular dysfunction in diabetic nephropathy

Test name	Use
Blood urea nitrogen (serum or plasma)	Initial diagnosis of acute or chronic kidney disease
Method: Spectrophotometry
Creatinine (serum or plasma)	Initial diagnosis of acute or chronic kidney disease
Method: Spectrophotometry
Microalbumin (urine)	May be used as a screening test
Method: Immunoturbidimetric	Useful in diabetic patients to assess baseline renal function
	Useful in monitoring diabetic nephropathy in insulin-dependent diabetes mellitus
Creatinine based glomerular filtration rate (estimated)	Estimate renal function and use as monitoring tool
Method: Spectrophotometry	(Test reports serum creatinine reference intervals)
Cystatin-C based glomerular filtration rate (estimated)	May be useful sensitive marker of renal disease; however, test lacks specificity due to reference range inavailability
Method: Nephelometry
Retinol-binding protein 4 (RBP4)	May be used as a marker for early diabetic nephropathy. Limited studies are available
Method: Non-commercial enzyme-linked immunosorbant assay (ELISA)
Adiponectin	Shown inverse correlation with renal dysfunction in type 2 diabetes
Method: Competitive radioimmunoassay
Connective tissue growth factor (CTGF)	CTGF excretion is correlated inversely with GFRs
Method: ELISA
Alpha-1-microglobulin (urine)	May indicate renal involvement in diabetic patients
Method: Nephelometry
Liver type fatty acid binding protein (L-FABP)	Expressed in proximal tubular cells and may associated with severity of diabetic nephropathy. Larger conclusive studies are required
Method: ELISA

Table 2 Expected results for microalbuminuria

Tests	Normal	Microalbuminuria	Macroalbuminuria
24 hr protein (mg)	< 150	< 500	≥ 500
24 hr albumin (mg)	< 30	30-300	> 300
Timed collection for albumin (μg/min)	< 20	20-200	> 200
Spot sample collection for albumin (μg albumin/mg creatinine)	< 30	30-300	> 300