A simple and inexpensive screening test for low protein levels in urine

Nigrosin binds to proteins yielding a dark blue complex. This reaction is used for detecting low protein concentrations in urine by applying spots of urine to cellulose acetate strips which are coloured by nigrosin. The intensity of coloured spots remaining after washing of the strips indicates protein concentration. With a cut-off at 50 mg protein/l, the test offers an excellent possibility for first line screening for microalbuminuria at lowest cost.