Method Description

Sodium, Potassium, Chloride:

Ion-selective electrode (ISE) (indirect potentiometry). The ion selective electron (ISE) module indirectly measures the electromotive force (EMF) difference between an ISE and a reference electrode.  The EMF of the ion-selective electrode is dependent on the ion concentration of the sample. The EMF of the reference electrode is constant. An electronic calculation circuit converts EMF of the sample to the ion concentration of the sample.(Package insert: ISE Indirect Na, K, CL for Gen2. Roche Diagnostics; 12/2020)

Bicarbonate:

This is a photometric rate reaction. Bicarbonate (HCO3-) reacts with phosphoenolpyruvate (PEP) in the presence of phosphoenolpyruvate carboxylase (PEPC) to produce oxaloacetate and phosphate. The oxaloacetate produced is coupled with NADH in the presence of malate dehydrogenase (MDH) to produce malate and NAD. The consumption of NADH causes a decrease in absorbance and is monitored in the UV range of 320 nm to 400 nm. The rate of change is directly proportional to the concentration of bicarbonate.(Package insert: Bicarbonate reagent Roche Diagnostics; 04/2019)

Anion Gap:

This is a calculated result. The following equation is used to calculate the anion gap (A gap):

A gap =Na - (Cl + HCO3-)

Blood Urea Nitrogen:

This is a kinetic UV assay where urease cleaves urea to form ammonia and carbon dioxide. The ammonia formed then reacts with alpha-ketoglutarate and NADH in the presence of urease/glutamate dehydrogenase to yield glutamate and NAD+. The decrease in absorbance, due to the consumption of NADH, is measured kinetically and is proportional to the amount of urea in the sample.(Package insert: Urea/BUN reagent. Roche Diagnostics; 12/2019)

Creatinine:

This enzymatic method is based on the conversion of creatinine with the aid of creatininase, creatinase, and sarcosine oxidase to glycine, formaldehyde, and hydrogen peroxide. Catalyzed by peroxidase the liberated hydrogen peroxide reacts with 4-aminophenazone and HTIB (hydroxy[tosyloxy]iodobenzene) to form a quinone imine chromogen. The color intensity of the quinone imine chromogen formed is directly proportional to the creatinine concentration in the reaction mixture.(Package insert: Creatinine. Roche Diagnostics; 02/2019)

Calcium:

Calcium ions react with NM-BAPTA (5-nitro-5'-methyl-1,2-bis[o-aminophenoxy]ethane-N,N,N',N'-tetraacetic acid) under alkaline conditions to form a complex. This complex reacts in the second step with EDTA. The change in absorbance is directly proportional to the calcium concentration and is measured photometrically.(Package insert: Calcium Gen.2 reagent. Roche Diagnostics; 07/2019)

Glucose:

Glucose in the serum, in the presence of hexokinase, is converted to glucose-6-phosphate (G6P). In the presence of nicotinamide adenine dinucleotide phosphate (NADP+), glucose-6-phosphate dehydrogenase oxides G6P to gluconate-6-phosphate and NADPH. The rate of NADPH formation is directly proportional to glucose concentration and is measured photometrically.(Package insert: Glucose HK Gen.3 Reagent. Roche Diagnostics; 11/2021)

Total Protein:

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: Total Protein Gen.2 reagent, Roche Diagnostics; 11/2019)

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: Albumin Gen.2 reagent. Roche Diagnostics; 02/2022)

Aspartate Aminotransferase:

Aspartate aminotransferase (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: AST reagent. Roche Diagnostics; 02/2022)

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: Alkaline Phosphatase Gen.2 reagent. Roche Diagnostics; 04/2019)

Alanine Aminotransferase:

Alanine aminotransferase (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: ALT reagent. Roche Diagnostics; 11/2021)

Total Bilirubin:

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. Roche Diagnostics; 01/2020)