CHAPTER 6: CHEMICAL EXAM OF URINE Flashcards
Provide a simple, rapid means for performing medically significant chemical analysis of urine, including pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocytes, and specific gravity
Reagent strips
This technique ensures the prevention of urine run-over while comparing it with the color chart.
(1) Blotting the edge of the strip on absorbent paper
(2) Holding the stirp horizontally
Recommended storage temperature of reagent strips according to manufacturers.
Room temperature below 30oC (but never refrigerated)
Reagent strips must be checked with both positive and negative controls a minimum of once every _______________ hours.
24 hours
True or False.
Distilled water is a recommended negative control.
False.
Defined as test using different reagents or methodologies to detect the same substances as detected by the reagent strips with the same or greater sensitivity or specificity
Confirmatory Tests
Major regulators of the acid-base content in the body
Lungs and Kidneys
Normal pH for
1) Random urine
2) 1st morning urine
1) Random urine - 4.5 to 8.0
2) 1st morning urine - 5.0 to 6.0 (slightly acidic)
pH of unpreserved urine
9.0
An aid in determining the existence of systemic acid–base disorders of metabolic or respiratory origin and in the management of urinary conditions
pH
a. acidic urine
b. alkaline urine
1) Respiratory/ metabolic acidosis not related to renal function disorders
2) Respiratory or metabolic alkalosis is present
1) Respiratory/ metabolic acidosis not related to renal function disorders
- Acidic urine
2) Respiratory or metabolic alkalosis is present
- Alkaline urine
A urinary crystal that is a frequent constituent of renal calculi that precipitates primarily in acidic and not alkaline urine
calcium oxalate
Urinary pH is controlled primarily by ___________________, although medications also
may be used.
Dietary regulation
a. acidic urine
b. alkaline urine
1) Fruits and vegetables
2) High-protein and high-meat diets
1) Fruits and vegetables (except cranberry juice)
- alkaline urine
2) High-protein and high-meat diets
- acidic urine
A pH above __________ is associated with an improperly preserved specimen and indicates that a fresh specimen should be obtained to ensure the validity of the analysis
8.5
Principle of pH
Double indicator system of Methyl Red and Bromthymol Blue
1) Methyl red produces a color change from
red to yellow in the pH range _________;
2) Bromthymol blue turns from yellow to blue in the pH range of ________.
1) Methyl Red (Red to Yellow) - 4 to 6
2) Bromthymol Blue (Yellow to blue) - 6 to 9
Most indicative of renal disease
Protein determination
Often associated with early renal disease
Proteinuria
Due to its low molecular weight, __________is the major serum protein found in normal urine
albumin
NV of protein found in urine
<10mg/dL or <100mg/24 hours
Caused by conditions affecting the plasma prior to its reaching the kidney and, therefore, is not indicative of actual renal disease.
Prerenal proteinuria
A proliferative disorder of the immunoglobulin-producing plasma cells
Multiple Myeloma
In multiple myeloma, the serum contains markedly elevated levels of monoclonal immunoglobulin light chains referred to as _____________.
Bence Jones Protein
Indication of proteinuria that occurs during the latter months of pregnancy
Pre-eclamptic state
Onset of renal complications can first be predicted by detection of ___________. Its presence is also associated with an increased risk of CVD
microalbuminuria
Occurs following periods spent in a vertical posture and disappears when a horizontal position is assumed.
Increased pressure on the renal vein when in the vertical position is believed to account for this condition.
Orhtostatic Proteinuria (Postural)
If orthostatic proteinuria is present,
1) First morning spx -
2) Second spx -
a. Positive reading
b. Negative reading
If orthostatic proteinuria is present,
1) First morning spx - negative
2) Second spx - positive
Principle of protein reagent strip testing
Protein (Sorensen’s) error of indicators
The reagent strip testing for protein is more sensitive to _________ because it contains more amino groups to accept the hydrogen ions than other proteins.
albumin
At a pH level of 3, protein indicators would appear _________ in the absence of protein and __________ as the protein conc. increases.
yellow; green to blue respectively
Protein indicators
Tetrabromophenol blue
Tetrachlorophenol
Tetrabromosulfonpthalein
A cold precipitation test that reacts equally with all forms of protein.
Sulfosalicylic Acid (SSA) Test
All precipitation tests must be performed on ____________ specimens to remove any extraneous contamination.
centrifuged (specimens)
A strip containing a gold- labeled antihuman albumin antibody-enzyme conjugate that binds albumin.
Reagent Strips for Micral Test
Principle of the reagent strip for creatinine
Pseudoperoxidase activity of copper-creatinine complexes
Because of its value in the detection and monitoring of diabetes mellitus, this test is the most frequently performed chemical analysis on urine.
Glucose Test
Plasma concentration of a substance at which tubular reabsorptio stops and there is an increased amount of glucose in urine.
Renal threshold (approx. 160 - 180mg/dL)
Hyperglycemia that occurs during pregnancy and disappears after delivery
Gestational diabetes
This hormone’s primary function is to convert glucose to glycogen for storage.
Insulin
A strong inhibitor of insulin secretion and is increased when the body is subjected to severe stress, which accounts for the glucosuria seen in conjunction with cerebrovascular trauma and myocardial infarction.
Epinephrine
Reagent strips for glucose are impregnated with these mixture to produce a double sequential enzyme reaction.
Glucose oxidase
Peroxidase
Chromogen
Buffer
For glucose test pads, this chemical is incorporated, oxidizing ascorbic acid, so that it cannot interfere with the oxidation of the chromogen which may produce false-negative results
Iodate
Greatest source of false-negative glucose
results
Allowing specimens to remain unpreserved at room temperature for extended periods
This test for glucose relies on the ability of glucose and other substances to reduce copper sulfate (CuSO4) to cuprous oxide (Cu2O) in the presence of alkali and heat.
Clinitest (Copper Reduction Test)
Occurs if >2g/dL sugar is present in urine
Pass through phenomenon
This reducing sugar in the urine of a newborn represents an “inborn error of metabolism”
Galactose
The lack of this enzyme prevents breakdown of ingested galactose and results in failure to thrive and other complications, including death.
Galactose-1uridyltransferase
This reducing sugar is frequently found in the urine of nursing mothers
Lactose
(-) glucose oxidase
(+) clinitest
(+) nonglucose reducing substance
1+ glucose oxidase
(-) clinitest
True glycosuria
4+ glucose oxidase
(-) clinitest
False positive (oxidizing agent interference)
Result from increased fat metabolism due to inability to metabolize carbohydrate.
Ketones
Three intermediate products of fat metabolism represented by ketones
2% acetone
20% acetoacetic acid (parent ketone)
78% B-hydroxybutyrate (major ketone but not detected)
Used for insulin dosage monitoring
Ketones
Shows a deficiency in insulin, indicating the need to regulate dosage
ketonuria
A nonreducing sugar that does not react with Clinitest or glucose oxidase strips
sucrose
Confirmatory test for ketones
Acetest
Provided by Acetest in tablet form
Sodium Nitroprusside
Glycine
Disodium phosphate
Lactose
(1) Blood present in the urine in the form of intact RBC
(2) Product of RBC destruction
(1) Blood present in the urine in the form of intact RBC - Hematuria
(2) Product of RBC destruction - hemoglobinuria
1) Produces a cloudy red urine
2) Clear red urine w/ reddish plasma
3) Clear red urine w/ clear plasma
1) Produces a cloudy red urine
- Hematuria
2) Clear red urine w/ reddish plasma
- Hemoglobinuria
3) Clear red urine w/ clear plasma
- Myoglobinuria
Amount of blood in urine considered as clinically significant
> 5 cells per microliter
Result from the lysis of red blood cells produced in the urinary tract, particularly in dilute, alkaline urine.
Hemoglobinuria
(+) Hemoglobinuria
Decreased haptoglobin and hemopexin
Intravascular Lysis
Reabsorption of filtered hemoglobin results in the appearance of large yellow-brown granules of denatured ferritin called ____________.
hemosiderin
heme-containing protein found in muscle tissue,
not only reacts positively with the reagent strip test for blood
but also produces a clear red-brown urine
A heme-containing protein found in muscle tissue that produces a clear red-brown urine
Myoglobin
Myoglobinuria is associated with muscle destruction known as _________.
rhabdomyolysis
1) Uniform green/blue appearance on pad
2) Speckled pattern
a. Hemoglobinuria
b. Myoglobinuria
c. Hematuria
1) Uniform green/blue appearance on pad
- Hgb/Mgb
2) Speckled pattern
- Hematuria
A bacteria that causes false positive reactions in blood strip test
E. coli
Provide an early indication of liver disease
Bilirubin
A highly pigmented yellow compound; a degradation product of hemoglobin
Bilirubin
Where RBCs are destroyed by phagocytic cells
spleen and liver
Components of hemoglobin
Iron, Protein, Protoporphyrin
Where bilirubin is reduced by bacteria to urobilinogen, which is then oxidized and excreted in the feces in the form of stercobilinogen and urobilin.
intestine
This is the only type of bilirubin that can appear in the urine when the normal degradation cycle is disrupted by bile duct obstruction.
conjugated bilirubin
Bilirubin combines with these reagents in an acid medium to produce an azodye
2,4 - dichloroanilinine diazonium salt
2,6 - dichlorobenzene diazonium salt
An unstable compound that is rapidly photo-oxidized to biliverdin when exposed to light
Bilirubin
True or false.
Biliverdin reacts with diazo reaction
False
Confirmatory test for bilirubin
Ictotest
Positive result (color) in Ictotest tablets
blue to purple
Pigments responsible for characteristic brown color of feces
Stercobilin and Urobilin
For early detection of liver disease
Urobilinogen
1) Soluble to both chloroform and butanol
2) Insoluble to both chloroform and butanol
a. Porphobilinogen
b. Urobilinogen
1) Soluble to both chloroform and butanol
- Urobilinogen
2) Insoluble to both chloroform and butanol
- Porphobilinogen
A rapid screening test for the presence of UTI designed to detect cases in which the need for culture may not be apparent (but not designed to replace culture)
Nitrite
A test valuable for detecting initial bladder infection (cystitis)
Nitrite
An inflammatory process of the kidney and adjacent renal pelvis, is a frequent complication of untreated cystitis
Pyelonephritis
Detects nitrate in which nitrite at an acidic pH reacts with an aromatic amine to form a diazonium compound that then reacts with tetrahydrobenzoquinolin compounds to produce a pink-colroed azodye
Greiss Reaction
Standardized quantitative bacterial culture criterion of organisms per milliliter for nitrite.
100,000 (>100,000: UTI)
Bacteria that lack this enzyme do not possess the ability to reduce nitrate to nitrite.
Reductase
Reductase is found in the gram-____________ bacteria that most frequently cause UTIs.
gram neg (enterobacteriaceae)
When should nitrite be performed?
First morning or spx collected after urine has remained in the bladder for at least 4 hours
Offers a more standardized means for the detection of leukocytes.
Leukocyte Esterase
LE test detects the presence of esterase in the granulocytic white blood cells, except:
Lymphocytes
True or False.
Esterases are also present in Trichomonas and histiocytes
True
Other than lymphocytes, what else do not contain esterases?
erythrocytes, bacteria, renal tissue cells
Used to catalyze the hydrolysis of an acid ester embedded on the reagent pad to produce an aromatic compound and acid
LE
Crenation of leukocytes preventing release of esterases may occur in urines with a ______specific gravity.
a. low
b. high
b. high specific gravity
Based on the change in pKa (dissociation constant) of a polyelectrolyte in an alkaline medium.
Specific Gravity
Urine concentration = high
Hydrogen ions = increased
pH = ?
low pH
Type of solute measured by specific gravity reagent strip that eliminates the interference by the large organic molecules (urea and glucose)
ionic solutes
