The ratio usually is reported in milligrams of albumin to grams of creatinine. There are several diagnostic methods currently in use for measuring urine proteins. These differ in method principles, means of calibration and types of instrumentation. Dye binding methods are based on the property of proteins to bind dyes such as Coomassie Brilliant Blue and Pyrogallol Red. These properties can be used to stain protein bands after electrophoresis, as well as in quantitative assays, if calibration is performed with known protein standards.
Dye binding methods measure total protein but lack specificity for albumin.
They primarily are manual methods and tend not to be used as much as they were in the past. Albumin in the urine competes with radioactive labeled albumin for limited antibody bonding sites. After incubation, the bound antibody is precipitated and the unbound albumin in the supernatant is removed. The remaining radioactive pellet is counted in a gamma counter. The amount of radioactivity in patient samples is compared to a calibration curve developed using known amounts of albumin.