Reagent Strip Parameter Flashcards

Flashcards covering the principles, reagents, sensitivities, and interferences of urinalysis reagent strip parameters based on lecture notes.

Glucose Reagent Principle

Double Sequential Enzyme reaction utilizing Glucose oxidase and peroxidase.

Glucose Reaction Equations

$Glucose + O_2 \rightarrow Gluconic acid + H_2O_2$ followed by $H_2O_2 + Chromogen \rightarrow \text{Oxidized chromogen}$

Glucose Multistix Sensitivity

$$75 \text{ to } 125\,mg/dL$$

Protein Error of Indicator (Sorensen's)

A principle where an indicator changes color due to protein presence rather than pH; uses tetrabromphenol blue (Multistix) or tetrachlorophenol tetrabromosulfonphthalein (Chemstrip) in pH 3 citrate buffer.

Blood Reagent Principle

Pseudoperoxidase Activity of HGB where hemoglobin catalyzes the reaction between $H_2O_2$ and the chromogen tetramethylbenzidine.

Specific Gravity Principle

Based on the change in the $pK_a$ (dissociation constant) of a polyelectrolyte in relation to ionic concentration.

Specific Gravity Polyelectrolytes

Ethylene glycol-bis tetraacetic acid (Chemstrip) or polymethylvinyl ether/maleic acid (Multistix) with Bromthymol blue indicator.

pH Double Indicator System

Methyl Red ($pH\,4-6$: Red to Yellow) and Bromthymol blue ($pH\,6-9$: Yellow to Blue).

Sodium Nitroprusside Reaction

The principle used to detect Ketones (specifically acetoacetic acid); uses Sodium Nitroprusside, Disodium phosphate buffer, and Glycine to detect acetone.

Diazo Reaction

The principle for Bilirubin detection; Bilirubin + Diazonium salt (Dichloroaniline or Dichlorobenzene tetrafluoroborate) $\rightarrow$ Acid azo dye.

Urobilinogen Reagent Principles

Multistix uses EHRLICH’S REACTION ($p\text{-diethylaminobenzaldehyde}$), while Chemstrip uses AZO COUPLING (4-methoxybenzene diazonium tetrafluoroborate).

Greiss Reaction

The principle for Nitrite detection; Aromatic amine + Nitrite $\rightarrow$ Diazonium salt $\rightarrow$ Azo dye.

Leukocyte Esterase Reading Time

120 seconds

Ascorbic Acid Interference Mechanism

Ascorbic acid readily oxidizes to dehydroascorbic acid and causes FALSE-NEGATIVE results in tests using $H_2O_2$ or diazonium salts, including Blood, Bilirubin, LE, Nitrite, and Glucose.

Protein False Positive Factors

Highly buffered alkaline urine, pigmented specimens, quaternary ammonium compounds, antiseptics, chlorhexidine, loss of buffer, or high specific gravity.