Method Description

Bilirubin, Total:

Total bilirubin, in the presence of a suitable solubilizing agent, is coupled with 3,5-dichlorophenyl diazonium in a strongly acidic medium. The color intensity of the red azo dye formed is directly proportional to the total bilirubin and can be determined photometrically.(Package insert: Bilirubin Total Gen. 3, 07/2014. Roche Diagnostics, Indianapolis, IN)

Bilirubin, Direct:

Acidified sodium nitrite produces nitrous acid which reacts with sulfanilic acid (in acidic solution) to form a diazonium salt. The diazotized sulfanilic acid then reacts with bilirubin to form isomers of azobilirubin. In the direct bilirubin assay, only conjugated bilirubin is converted by the diazotized sulfanilic acid. The intensity of the color of azobilirubin is measured photometrically at 570 nm and is proportional to the direct (conjugated) bilirubin concentration.(Package insert: Roche Direct Bilirubin reagent; Indianapolis, IN, October 1999)

Aspartate Aminotransferase (AST):

AST is measured by a coupled enzyme kinetic method where the rate of decrease of NADH, determined at 340 nm, is directly proportional to the AST activity.(Package insert: Roche AST reagent, Indianapolis, IN, January 2000)

Alanine Aminotransferase (ALT):

ALT activity is determined by a kinetic method using a coupled enzyme reaction where the rate of NADH consumption is measured at 340 nm. The NADH decrease is directly proportional to the ALT activity.(Package insert: Roche ALT reagent, Indianapolis, IN, January 2000)

Alkaline Phosphatase:

In the presence of magnesium and zinc ions, p-nitrophenyl phosphate is cleaved by phosphatases into phosphate and p-nitrophenol. The p-nitrophenol released is directly proportional to the catalytic alkaline phosphatase activity. It is determined by measuring the increase in absorbance.(Package insert: Roche Alkaline Phosphatase reagent, Indianapolis, IN, February 2012)

Albumin:

The dye, bromcresol green (BCG), is added to serum in an acid buffer. The color intensity of the blue-green albumin-BCG complex is directly proportional to the albumin concentration and is determined photometrically.(Package insert: Roche Albumin reagent; Roche Diagnostic Corp., Indianapolis, IN, July 1999)

Protein, Total:

Divalent copper reacts in alkaline solution with protein peptide bonds to form the characteristic purple-colored biuret complex. Sodium potassium tartrate prevents the precipitation of copper hydroxide and potassium iodide prevents autoreduction of copper. The color intensity is directly proportional to the protein concentration which can be determined photometrically.(Package insert: Roche Protein reagent, Roche Diagnostic Corp., Indianapolis, IN 1999)