Urine Glucose Reagent Strip Parameters

Study Notes

Quality Control for Reagent Strips

Run quality control when opening a new bottle or when obtaining questionable results
Manual methods can be done using tablets or liquid chemicals when questionable results are obtained or when the urine is highly pigmented

Urine Glucose

Double sequential enzymatic reaction involves two enzymes: glucose oxidase and peroxidase
Reagent strip contains a mixture of glucose oxidase, peroxidase, chromogen (indicator), and buffer
Procedure:
- Mix urine specimen thoroughly
- Never allow strip to remain in urine for extended periods
- Never forget to blot the edge of the strip after dipping
- Compare color reactions of the dipstick with the color chart horizontally
- Use good light source
- Never interchange reagents strips and color charts from different manufacturers
- Allow refrigerated specimen to return to room temperature before using reagent strips
- Protect reagent strips from deterioration caused by moisture, volatile chemicals, heat, and light
- Store at room temperature below 30°C, but never refrigerated
- Never use past the expiration date

Reaction Interferences

False (+) results can occur due to:
- Hydrogen peroxide
- Urine container contaminated with detergents
False (-) results can occur due to:
- Ascorbic acid
- High level of ketones
- High specific gravity of urine
- Low temperature
- Prolonged standing of urine

Copper Reduction Tests for Glucose

Rely on the ability of glucose and other reducing substances to reduce copper sulfate to cuprous oxide in the presence of alkali and heat
Color change from negative blue to green, yellow, orange, and red
Tests that utilize this principle:
- Benedict's Test
- Copper sulfate
- Sodium carbonate
- Sodium citrate buffer

Chemical Examination of Urine

Chemical examination of urine validates physical aspects of urine analysis
Reagent strips (dipsticks) are a sensitive and rapid procedure
Reagent strip:
- Narrow strip of plastic with small pads attached to it
- Each pad contains reagents for different reactions, allowing for simultaneous determination of several tests
- Colors generated are compared against a brand-specific color chart

Technique for Using Reagent Strips

Dip reagent strip briefly into well-mixed urine at room temperature
Remove excess urine by touching the edge of the strip to the container upon withdrawal
Blot the edge of the strip into an absorbent pad
Wait for the specified amount of time
Compare the color reaction of each pad to the manufacturer's color chart
Run with positive and negative controls every 24 hours at the beginning of each shift

Urine Protein

Protein error indicators:
- Tetrabromphenol blue
- Tetrachlorophenol or Tetrabromsulfonphthalein
Acidic buffer maintains pH of indicators at 3.0, giving them yellow coloration in the absence of proteins
Proteins (primarily albumin) accept hydrogen ions from the indicator, altering the pH and turning the color from yellow to green to blue, depending on the amount of proteins
Color is reported in terms of negative, trace, 1+, 2+, 3+, 4+

Renal Proteinuria

Glomerular proteinuria:
- Selective filtration is impaired due to damage in glomerulus (e.g., lupus, erythematosus, and streptococcal glomerulonephritis)
Tubular proteinuria:
- Tubular dysfunction (e.g., heavy metal poisoning, Fanconi syndrome, and viral infection)
Microalbuminuria:
- Development of diabetic nephropathy and cardiovascular disease
Orthostatic/postural proteinuria:
- Physiologic type due to prolonged standing, increased glomerular pressure, and ability of proteins to cross over
- Common in jobs that require prolonged standing

Description

Learn about urine glucose reagent strip parameters and the double sequential enzymatic reaction used for glucose detection. Understand the enzymes involved and the process of catalyzing glucose reaction on the reagent strip.