Chemical Examination Flashcards by Janaine Balagot Pesiao

Reagent strips enable rapid screening of urine specimens for:

✓pH
✓Protein
✓Glucose
✓Ketones
✓Blood
✓Bilisrubin
✓Urobilinogen
✓Nitrite
✓Leukocyte esterase

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Routinely used for chemical analysis of urine.

Reagent strips

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Four commonly used brands of commercial reagent strips are:

✓Multistix (Siemens Healthcare Diagnostics Inc., Deerfield, IL)
✓Chemstrips (Roche Diagnostics, Indianapolis, IN)
✓vChemStrips (Iris Urinalysis-Beckman Coulter Inc., Brea, CA)
✓Aution Sticks (Arkray Inc., Kyoto, Japan) 3

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commercial _____ or _____ consists of reagent impregnated test pads that are fixed to an inert plastic strip

reagent strip or dipstick

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Reducing agents such as _____ have the potential to adversely affect several reagent strip test results

Ascorbic acid

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reporting of reagent strips:
The ____ and the ____are exceptions; these results are estimated in their respective units.

specific gravity, the pH

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REAGENT STRIP
Results are reported (depending on the test):

✓In concentration (milligrams per deciliter)
✓As small, moderate, or large
✓Using the plus system (1+, 2+, 3+, 4+)
✓As positive, negative, or normal

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Reagent strips have significantly:

Reduced the time required for testing
Reduced costs (e.g., reagents, personnel)
Enhanced test sensitivity and specificity
Decreased the amount of urine required for testing

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To ensure the integrity of reagent strips, their ____ is essential, and the manufacturer’s directions must be followed.

proper storage

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REAGENT STRIPS Care and Storage
❑All reagent strips must be protected from ____, ____, ____, and ____.
❑Any strips showing evidence of deterioration,
contamination, or improper storage should be ______.
❑Tight-fitting lids, along with desiccants or drying agents within the product container, help eliminate test pad _____ due to _____.

moisture, chemicals, heat, and light
discarded
deterioration, moisture

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REAGENT STRIPS Care and Storage
❑Fumes from volatile chemicals, acids, and bases can adversely affect the test pads and should be avoided.
❑All reagent strip containers protect the reagent strips from____ and ____; however, the containers themselves must be protected to prevent fading of the color chart located on the label of the container.
❑Reagent strips should be stored in their original containers at temperatures below ____; they are stable until the expiration date indicated on the label.

ultraviolet rays, sunlight
30°C (86°F)

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✓Ensures that the reagent strips are functioning properly.
✓Confirms the acceptable performance and technique of the laboratorian using them.

Quality Control Testing

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Quality Control Testing:
____ and ____ control levels must be used to check the
reactivity of reagent strips.

negative and positive control

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Quality Control Testing:
____ or ____ can serve as acceptable negative/positive controls.

Commercial or laboratory-prepared materials

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aliquoting a well-mixed urine specimen from the daily workload and having a different laboratory analyze the specimen.

Interlaboratory

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aliquoting a well-mixed urine specimen from the daily workload and having a technologist on each shift analyze the specimen.

Intralaboratory

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_____ duplicate testing can also be used to evaluate the technical competency of
laboratorians.

Intralaboratory

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____ duplicate testing checks the entire urinalysis procedure and detects innocuous changes when manual urinalyses are performed, such as variations in the speed of centrifugation and in centrifuge brake usage.

Interlaboratory

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TABLET AND CHEMICAL TESTS
Care and Storage:
➢Susceptible to deterioration from
exposure to ____, ____, and ____.

light, heat, and moisture.

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CHEMICAL TESTS
✓ ____ – detect protein
✓ ____ – detect porphobilinogen (PBG)
✓ ____ – detect porphyria
✓ ____ – detect glucose

✓Sulfosalicylic acid (SSA) precipitation test
✓Hoesch test
✓Watson-Schwartz test
✓Benedict’s test

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When new reagents are prepared, they should be tested in _____ to ensure equivalent performance.

parallel with current “in-use” reagents

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Urine specimen (room temperature) – it must be tested within ____ after collection to avoid erroneous results caused by changes that can occur in unpreserved urine

2 hours

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Urine specimen (Refrigerated) – it should be allowed to ____ before testing with reagent strips to avoid erroneous results

warm up to room temperature

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Urines that are highly pigmented due to medications can lead to_____ reagent strip test results because the true color reaction is masked by the pigment present.

false-positive

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Cite the 10 CHEMICAL TEST

✓Specific Gravity ✓pH ✓Protein ✓Blood ✓Leukocyte Esterase ✓Nitrite ✓Glucose ✓Ketones ✓Bilirubin and Urobilinogen ✓Ascorbic Acid

*Specific Gravity Clinical Significance ___ same as pure water; suspect adulteration of urine specimen

1.000

*Specific Gravity Clinical Significance ___ indicates presence of iatrogenic substance (e.g., radiographic contrast media, mannitol) (physiologically impossible)

>1.040

*Specific Gravity Clinical Significance ___ Indicates average solute and water intake and excretion

1.010–1.025

*Specific Gravity Clinical Significance ___ Dilute urine; associated with increased water intake or water diuresis (e.g., diuretics, inadequate secretion/action of ADH*)

1.001–1.009

*Specific Gravity Clinical Significance ___ Concentrate urine; associated with dehydration, fluid restriction, profuse sweating, osmotic diuresis

1.025–1.035 (1.040 maximum)

*Specific Gravity Principle Ionic solutes present in the urine cause protons to be released from a polyelectrolyte. As protons are released, the pH decreases and produces a color change of the ____ indicator from ____ to ____

- bromthymol blue - blue-green to yellow-green

*Specific Gravity Principle ❑Specificity * Detects only ____; provides “estimate” in 0.005 increments

- ionic solutes

*pH Clinical Significance ❑Urine pH varies from ____ ❑Average individual excretes slightly acidic urine of pH ____

- 4.5 to 8.0 - 5.0 to 6.0

*pH Clinical Significance ___ suspect adulteration of urine specimen.

<4.5

*pH Clinical Significance ___ indicates: * Presence of an iatrogenic alkaline substance (intravenous medication or agent) * Improperly stored urine specimen * Contamination with an alkaline chemical (preservative)

>8.0

*pH Clinical Significance ___ associated with: * Diet (high protein and cranberry ingestion) , sleep, metabolic acidosis (e.g., ketoacidosis, starvation, severe diarrhea, uremia, poisons—ethylene glycol, methanol), respiratory acidosis (e.g., emphysema, chronic lung disease), urinary system disorders: UTI with acid-producing bacteria (Escherichia coli), chronic renal failure, uremia, medications used to induce: ammonium chloride, ascorbic acid, methionine, mandelic acid

4.5 - 6.9 (Acid urine)

*pH Clinical Significance associated with: * Diet(vegetarian, citrus fruits, low carbohydrate), metabolic alkalosis (e.g., vomiting, gastric lavage), respiratory alkalosis (e.g., hyperventilation), urinary system disorders: UTI with urease producing bacteria (Proteus sp., Pseudomonas sp.), renal tubular acidosis, medications used to induce: sodium bicarbonate, potassium citrate, acetazolamide

7.0 - 7.9 (Alkaline urine)

pH Reagent Strip Method ❑Principle: _____ * Indicators: ____ and ____ are used to give distinct color changes from ___ to ___ to ___ (pH 5.0–9.0). ❑Specificity: pH; _____ * No interferences known; unaffected by protein concentration

- Double-indicator system - methyl red and bromthymol blue, - orange to green to blue - hydrogen ion concentration

alternative method of pH test that consists of a silver–silver chloride indicator electrode

pH meter

CHEMICAL TESTS Protein Clinical Significance ➢Normal urine – ____ (1 to 14 mg/dL) of protein each day * one-third albumin and two-thirds globulins

150 mg

Proteins that originate from the urinary tract:

* Uromodulin (also known as Tamm-Horsfall protein) * Urokinase (enzyme) * Secretory immunoglobulin A

first indicator of renal disease (albumin).

Proteinuria

most common type of proteinuria encountered and is the most serious

Glomerular proteinuria

Proteinuria can be classified into four categories:

✓Prerenal or overflow proteinuria ✓Glomerular proteinuria ✓Tubular proteinuria ✓Postrenal proteinuria

an increase in plasma low MW proteins leads to increased excretion in urine.

Prerenal or overflow proteinuria

➢Normal proteins present in Prerenal or overflow proteinuria: __ __ __ ➢Abnormal proteins: __

- Myoglobin, Hemoglobin, Acute phase reactants - Ig light chains (Bence Jones protein – Multiple Myeloma)

*Protein Methods detects all proteins in urine—albumin and globulins.

Sulfosalicylic Acid Precipitation Test (SSA)

Sulfosalicylic Acid Precipitation Test (SSA) is not frequently performed today because it is ___ and ____

nonspecific and time-consuming

*PROTEIN Reagent Strip Tests Principle: ___ *Color change: ___ *Indicator used: ___ *Sensitivity: ___

- Protein error of indicators - from yellow to blue-green - tetrabromophenolblue - More sensitive to albumin

➢Monitoring of urine for low-level albumin. ➢Used for individuals with diabetes, hypertension, or peripheral vascular disease

Sensitive Albumin (Microalbumin) Tests

Determination of an _____ reduces the numbers of false positive and false-negative test results.

A/C or protein-to-creatinine ratio

*Blood Clinical Significance ❑ ____– abnormal quantity of red blood cells in the urine (Cloudy or smoky urine). ❑ ____– indicates the urinary presence of hemoglobin (Clear urine). ❑ ____– indicates the urinary presence of myoglobin.

- Hematuria - Hemoglobinuria - Myoglobinuria

*BLOOD Reagent Strip Tests Principle: ___ *Color change: ___ *Chromogen used: ___

- Pseudoperoxidase activity - from Yellow to green - tetramethylbenzidine

*Leukocyte Esterase Clinical Significance ❑Normal urine: ____ ❑Pathologic urine: ____

- 0 to 8 per hpf - 20 or more WBCs per microliter

*Leukocyte Esterase Reagent Strip Test Principle: ___ *Color change: ___ *Specificity: ___

- azo coupling reaction - from beige to violet - Detects only granulocytic leukocytes

Routine screening for urine nitrite provides an important tool to identify urinary tract infection.

Nitrite

___ are infecting the urinary tract and adequate bladder retention time is allowed, these bacteria convert dietary nitrate to nitrite

Nitrate-reducing bacteria

*Nitrite Reagent Strip Principle: ___ *Color change: ___

- Diazotization reaction followed by azo coupling reaction - from white to pink

presence of glucose in urine

Glucosuria

non-glucose sugars (e.g., fructose, sucrose, lactose) or a combination of sugars are present in urine

Glycosuria

is an inherited disorder characterized by an inability to metabolize galactose to glucose

Galactosemia

is the most common disease that causes hyperglycemia and glucosuria

Diabetes mellitus

*Glucose Reagent Strip Tests Principle: ___ *Specificity: ___

- Double-sequential enzyme reaction - Specific for glucose

method used for glucose

Copper Reduction Tests (Benedict’s test)

A tablet version of Benedict’s test

Clinitest reagent tablet

Reducing substances in urine that can cause positive copper reduction test:

* Sugars (Glucose, Fructose, Galactose, Lactose, Maltose, except sucrose) * Ascorbic Acid * Cysteine * Homogentisic acid

Ketone Formation ❑The terms ketones and ketone bodies identify three intermediate products of fatty acid metabolism:

✓Acetoacetate – 20% ✓β-hydroxybutyrate – 78% ✓Acetone – 2%

ketones are excreted in the urine, 70 mg/dL (the renal threshold level)

Ketonuria

Urine ketone excretion is about ____

20 mg/day

*Ketone Reagent Strip Tests Principle: ___ *Color change: ___ *Chemstrip and vChem reagent strips include ____ in the reaction pad, which enables the detection of acetone *Specificity: ____

- Legal’s test—nitroprusside reaction - from beige to purple - glycine - Does not detect β-hydroxybutyrate

Tablet test for the detection of ketones in urine is the ___

Nitroprusside Tablet Test (Acetest)

* orange-brown color of feces: * contribute to the color of urine

- Urobilin and stercobilin - Urobilinogen

abnormally increased amounts of bilirubin in urine.

Bilirubinuria

abnormally increased amounts of bilirubin in the blood.

Hyperbilirubinemia

the yellowish pigmentation of skin, sclera, tissues, and body fluids caused by bilirubin

Jaundice

*Bilirubin Reagent Strip Test Principle: ____ *Color change: ____ *Physical Examination: ____

- Azo coupling reaction - from light tan to beige or light pink - Foam test

* A tablet test for the detection of bilirubin in urine is the Ictotest method * Concentrations of bilirubin as low as ____ can be detected.

- Diazo Tablet Test (Ictotest Method) - 0.05 to 0.1 mg/dL

Specimen of choice for quantifying or monitoring of Urobilinogen

a 2-hour collection after the midday meal (i.e., 2 PM to 4 PM) “alkaline tide”

Urobilinogen is ____ in acid urine and easily photo-oxidizes to ____

- labile - urobilin

Used to qualitatively screen for urobilinogen.

Classic Ehrlich’s Reaction

*Urobilinogen Reagent Strip Tests Principle: ___ *Color change: ___ *Multistix strips: ___

- azo coupling reaction - from light pink to dark pink - modified Ehrlich’s reaction

is a strong reducing substance because of its ene-diol group.

Ascorbic acid

Ascorbic acid color change on Reagent strip

from blue to orange