[Differential diagnosis of proteinuria]

Normally, protein secretion in the urine is less than 150 mg/day or less than 100 mg/g creatinine. Orthostatic proteinuria, proteinuria in the presence of fever, and effort proteinuria are benign forms. In cases of persistent proteinuria, prerenal or overflow proteinuria are distinguished from renal and post-renal proteinuria. Renal forms can be differentiated into glomerular and tubular as well as mixed forms. The urine dipstick is of only low sensitivity, and is therefore unsuitable as a screening test for diabetic microalbuminuria. In addition, it cannot detect immunoglobulin light chains in Bence Jones proteinuria. For the differentiation between glomerular and tubular forms of proteinuria, the determination of marker proteins in the urine, for example, alpha1 microglobulin, albumin and IgG, has proven utility.