MIDTERM LEC: CHEMICAL EXAMINATION Flashcards
(165 cards)
1
Q
- composed of several chemical-impregnated
- absorbent pads attached to a plastic
- color producing chemical reaction takes place when absorbent pad comes in contact with urine
- reactions are interpreted by comparing the color produced on the pad with a chart supplied by the manufacturer
A
REAGENT STRIP
2
Q
TYPES OF REAGENT STRIP
A
- MULTISTIX
- CHEMSTRIP
3
Q
(Siemens Healthcare Diagnostics, Deerfield, IN)
A
MULTISTIX
4
Q
(Roche Diagnostics, Indianapolis, IN)
A
CHEMSTRIP
5
Q
PROCEDURE:
A
- Dip the reagent strip completely in the urine
- Remove excess urine from the strip by running the edge of the strip on the container when withdrawing it from the specimen
- Blot the strip horizontally on an absorbent medium pad
- Wait for the specified length of time for reactions to take place
- Compare the colored reactions against the
manufacturer’s chart using a good light source
6
Q
ERRORS CAUSED BY IMPROPER TECHNIQUE
A
✓ Formed elements such as RBC & WBC sink to the bottom of the specimen therefore it will be undetected in an unmixed specimen
✓ Allowing the strip to remain in the urine for an extended period may cause leaching of reagents from the pads
✓ Excess urine remaining on the strip after its removal from the specimen can produce over-run between chemicals on adjacent pads, producing distortion of the colors
✓ The timing of reactions should be followed; when precise timing can’t be achieved, the reactions
✓ should be read between 60 & 120 second
✓ A good light source is essential for accurate
interpretation of color reactions
✓ The strip must be held close to the color chart without actually being placed on the chart
✓ Reagent strips & color charts from different
manufacturers are not interchangeable
✓ Specimens that have been refrigerated must allow to return to room temperature prior to reagent strip testing
7
Q
HANDLING & STORAGE OF REAGENT STRIP
A
✓ Reagent strips must be protected from deterioration caused by moisture, heat, light, & volatile chemicals
✓ Reagents are packed in opaque containers with a desiccant to protect them from light & moisture
✓ Strips are removed just prior to testing, & the bottle is tightly resealed immediately
✓ Bottle should not be open in the presence of volatile fumes
✓ Reagents should be stored at room temperature but never refrigerated
✓ All bottles are stamped with an expiration date that represents the functional life expectancy of the reagent strips therefore it must not be used past the expiration date
✓ Care must be taken not to touch the chemical pads when removing the strips
✓ A visual inspection should be done each time a strip is used to detect deterioration even though the strips may still be within the expiration date
8
Q
QUALITY CONTROL OF REAGENTS STRIPS
A
✓ Reagent strips must be checked with both positive & negative controls a minimum of once every 24hrs, usually every start of the shift
✓ Testing is also performed when a new bottle is opened, questionable results are obtained, or when there is concern about the integrity of the reagent strip
9
Q
AUTOMATED REAGENT STRIP READERS
A
PRINCIPLE: REFLECTANCE PHOTOMETRY
10
Q
light reflection from the test pads decreases in
proportion to the intensity of color produced by the concentration of the test substance
A
PRINCIPLE: REFLECTANCE PHOTOMETRY
11
Q
The most common sugar in the urine
A
GLUCOSE
12
Q
should not be detected in normal urine
A
GLUCOSE
13
Q
Small amounts when present are detected by any sensitive test
A
GLUCOSE
14
Q
GLUCOSE RENAL THRESHOLD:
A
160-180 mg/dl
15
Q
commonly used as a screening test for possible DM or to monitor control of blood glucose in diabetes
A
GLUCOSE
16
Q
Other Sugars in Urine
* Identified by TLC:
A
- FRUCTOSE (Levulose)
- GALACTOSE
- LACTOSE (Glu+Gal)
- PENTOSE
- SUCROSE (NON-REDUCING SUGAR)
17
Q
increase fruits, honey, syrup,
fructose intolerance
A
FRUCTOSE(Levulose)
18
Q
increase in infants with galactosemia
A
GALACTOSE
19
Q
increase during pregnancy, lactation, strict milk diet, lactose intolerance
A
LACTOSE (Glu+Gal)
20
Q
– increase in benign essential pentosuria (Xylulose, Arabinose)
A
PENTOSE
21
Q
increase in intestinal disorders, sucrose intolerance
A
SUCROSE (non-reducing sugar)
22
Q
HYPERGLYCEMIA-ASSOCIATED
blood glucose:
urine glucose:
A
INCREASE; INCREASE
23
Q
RENAL-ASSOCIATED
blood glucose:
urine glucose:
A
NORMAL; INCREASE
24
Q
HYPERGLYCEMIA-ASSOCIATED CAUSES:
A
- DM
- PANCREATITIS
- ACROMEGALY
- CUSHING’S SYNDROME
- HYPERTHYROIDISM
- PHEOCHROMOCYTOMA
- STRESS
- GESTATIONAL DIABETES
25
RENAL-ASSOCIATED CAUSES:
* FANCONI SYNDROME
* ADVANCED RENAL DISEASE
* OSTEOMALACIA
* PREGNANCY
26
GLUCOSE REACTION TIME:
30 SECONDS
27
GLUCOSE PRINCIPLE:
DOUBLE SEQUENTIAL ENZYME
REACTION
28
REAGENTS FOR GLUCOSE
MULTISTIX:
Glucose oxidase and Peroxidase
29
REAGENTS FOR GLUCOSE
MULTISTIX
CHROMOGEN:
Potassium Iodide →
(𝑏𝑙𝑢𝑒 𝑡𝑜 𝑔𝑟𝑒𝑒𝑛 𝑡𝑜 𝑏𝑟𝑜𝑤𝑛)
30
REAGENTS FOR GLUCOSE
CHEMSTRIP:
Glucose oxidase and Peroxidase
31
REAGENTS FOR GLUCOSE
CHEMSTRIP
CHROMOGEN:
Tetramethylbenzidine →
(𝑦𝑒𝑙𝑙𝑜𝑤 𝑡𝑜 𝑔𝑟𝑒𝑒𝑛)
32
REAGENTSTRIP FOR GLUCOSE
FALSE-POSITIVE:
Contamination by oxidizing
33
REAGENTSTRIP FOR GLUCOSE
FALSE – NEGATIVE:
✓ high levels of ascorbic acid
✓ high levels of ketones
✓ high specific gravity
✓ low temperatures
✓ improperly preserved specimens
34
COPPERREDUCTION TEST (CLINITEST (TABLET)/BENEDICT’S TEST) PRINCIPLE:
Copper Reduction
35
ability of the glucose and other substances to
reduce copper sulfate to cuprous oxide in the presence of alkali and heat.
COPPERREDUCTION TEST (CLINITEST (TABLET)/BENEDICT’S TEST)
36
color change progressing from negative blue
through green, yellow, and orange/red occurs when reaction takes place
COPPERREDUCTION TEST (CLINITEST (TABLET)/BENEDICT’S TEST)
37
- NOTE: Observe the reaction closely , because at high glucose level “ pass through” phenomenon may occur.
COPPERREDUCTION TEST (CLINITEST (TABLET)/BENEDICT’S TEST)
38
COPPERREDUCTION TEST (CLINITEST (TABLET)/BENEDICT’S TEST)
PREVENT PASS THROUGH :
use 2 gtts urine
39
FALSE-POSITIVE : Reducing agents
- Clinitest tablet test follow the same principle with Benedict’s Test
- The classic Benedict's solution was developed in 1908 and contained copper sulfate, sodium carbonate, and sodium citrate buffer
40
GLUCOCE OXIDASE: 1+ POSITIVE
CLINETEST: ______
INTERPRETATION: ________
CLINETEST: negative
INTERPRETATION: small amount of glucose
41
GLUCOCE OXIDASE: NEGATIVE
CLINETEST: ______
INTERPRETATION: __
CLINETEST: positive
INTERPRETATION: non-glucose reducing substance possible interfering substances for reagent strip
41
GLUCOCE OXIDASE: 4+ POSITIVE
CLINETEST: ______
INTERPRETATION: __
CLINETEST: negative
INTERPRETATION: oxidizing agent interfere on reagent strip
42
DETECT: Conjugated Bilirubin(water soluble)
BILIRUBIN
43
provide an early indication of liver disease
BILIRUBIN
44
pigmented yellow compound from the breakdown of hemoglobin
BILIRUBIN
45
Amber urine (Tea Color)with yellow foam
BILIRUBIN
46
CLINICAL SIGNIFICANCE OF BILIRUBIN IN URINE:
* Hepatitis
* Cirrhosis
* Other liver disease
* Biliary obstruction(gallstones, carcinoma)
47
REAGENTSTRIPFORBILIRUBIN(30 SECONDS)
PRINCIPLE:
Based on the “Diazo Reaction” of Bilirubin
48
BILIRUBIN
MULTISTIX:
2,4- dichloroaniline diazonium salt
49
BILIRUBIN
CHEMSTRIP:
2,6- dichlorobenzene diazonium
50
BILIRUBIN
FALSE- POSITIVE:
✓ Highly pigmented urines
✓ Phenazopyridine
✓ Indican
✓ Metabolites of iodine
51
BILIRUBIN
FALSE-NEGATIVE:
✓ Specimen exposure to light
✓ High conc. of nitrite
✓ Ascorbic acid
52
* More sensitive than reagent strip with less interference
* (+) blue to purple color
Contains:
✓ P- nitrobenzene-diazonium Ptoluenesulfonate
✓ SSA
✓ Sodium Carbonate
✓ Boric Acid
ICTOTEST (TABLET)
52
Result from increased fat metabolism due to inability to metabolize carbohydrates
KETONES
53
end product of rapid or excessive fatty acid breakdown when glucose is not used as source of energy
KETONE BODIES
54
KETONE BODIES:
* Beta-hydroxybutyric acid(78%)
* Acetoacetic acid(AAA)/Diacetic
acid (20%)
Acetone(2%)
55
major ketone but not detected in
reagent strip
Beta-hydroxybutyric acid(78%)
56
parent ketone
Acetoacetic acid(AAA)/Diacetic
acid (20%)
57
detected only when glycine is present
Acetone(2%)
58
CLINICAL SIGNIFICANCE OF KETONES IN URINE:
* Type 1 DM
* Insulin Dosage Monitoring
* Starvation
* Strenuous Exercise
* Malabsorption
* Vomiting
59
REAGENTSTRIP FOR KETONES(40 SECONDS)
PRINCIPLE:
Based on “NITROPRUSSIDE” reaction for ketones
60
KETONES REAGENT
CHEMSTRIP:
Sodium Nitroprusside(Sodium
Nitroferricyanide), Glycine
61
The ketone pad on the multi-reagent dip stick
detects mainly acetoacetic acid and acetone;
_________ is not detected.
ß-hydroxybutyrate
62
KETONES
FALSE-POSITIVE:
✓ Pthalein dyes
✓ Highly pigmented red urine
✓ Levodopa
✓ Medications containing free sulfhydryl groups
63
KETONES
FALSE- NEGATIVE:
✓ Improperly preserved specimens
64
CONTAINS:
✓ Sodium Nitroprusside
✓ Disodium Phosphate
✓ Lactose
ACETEST (TABLET)
65
* Density of the solution compared with density of similar volume of distilled water at a similar temperature
* Influenced by number and size of particles in a solution
SPECIFIC GRAVITY
66
REAGENTSTRIP FOR SPECIFIC GRAVITY(45 SECONDS)
* PRINCIPLE:
Change in pKa (dissociation constant) of polyelectrolyte
66
SPECIFIC GRAVITY CLINICAL SIGNIFICANCE:
* Monitoring Patient hydration and dehydration
* Loss of renal tubular concentrating ability
* Diabetes Insipidus
* Determination of unsatisfactory specimens
due to low concentration
67
- the polyelectrolyte ionizes, releasing hydrogen ions in proportion to the number of ions in the solution.
- reagent is sensitive to the no. ions in urine, indicator changes color in relation to ionic concentration
REAGENTSTRIP FOR SPECIFIC GRAVITY(45
SECONDS)
* PRINCIPLE: Change in pKa (dissociation constant) of polyelectrolyte
68
SPECIFIC GRAVITY REAGENT
CHEMSTRIP:
Ethyleneglycoldiaminoethylethertetraacetic bromthymol blue
68
SPECIFIC GRAVITY REAGENT
MULTISTIX:
Poly (methyl vinyl ether/ maleic
anhydride) bromthymol blue
69
SPECIFIC GRAVITY
FALSE-POSITIVE:
High concentration of protein
70
SPECIFIC GRAVITY
FALSE-NEGATIVE:
Highly alkaline urines (greater than 6.5)
71
the most indicative of renal diseases
PROTEIN DETERMINATION
72
associated with renal disorder
PROTEINURIA
73
Urine contains very little protein:
100 mg/24 hrs or 10 mg/dl of urine
74
These protein –are of low molecular weight:
50,000- 60,000 traversing the glomerulus
75
major protein found in the urine
ALBUMIN
76
normal urinary albumin content is ___
low
77
Albumin presented to glomerulus is ___ filtered
not
78
Filtered albumin is reabsorbed by the____
tubules
79
ALBUMIN NORMAL VALUES:
< 10 mg/dL or 100
mg/24 hrs (Strasinger)
< 150 mg.24 hrs (Henry)
80
* produced by the renal tubular cells and protein from prostatic, seminal and vaginal secretions
* mucoprotein found in the matrix of renal tubular casts.
TAMM-HORSFALL (UROMODULIN)
81
Caused by conditions that affect the plasma prior to its reaching the kidney
PRE-RENAL PROTEINURIA(“before”)
82
PRE-RENAL PROTEINURIA(“before”)
* Intravascular hemolysis =
hemoglobin
83
PRE-RENAL PROTEINURIA(“before”)
* Muscle Injury =
myoglobin
84
PRE-RENAL PROTEINURIA(“before”)
Severe infection and inflammation =
HIGH APRs
85
proliferation of immunoglobulin-producing plasma cells (Bence-Jones Protein)
Multiple myeloma
86
immunoglobulin light chains
Bence-Jones Protein
87
Bence-Jones Protein
URINE:
precipitates at 40-60℃ (cloudy)
and dissolves at 100℃
88
Bence-Jones Protein
TESTS:
Serum electrophoresis, immunofixation electrophoresis
89
RENAL PROTEINURIA(“true renal disease”)
A. GLOMERULAR PROTEINURIA:
1. DIABETIC NEPHROPHATHY
2. ORTHOSTATIC/CADET/ POSTURAL PROTEINURIA
90
* Decreased glomerular filtration
* May lead to renal failure
* INDICATOR: MICROALBUMINURIA = proteinuria undetectable by routine
reagent strip
DIABETIC NEPHROPHATHY
91
Proteinuria when standing
due to increases pressure to renal
veins
ORTHOSTATIC/CADET/ POSTURAL
PROTEINURIA
92
* Test for microalbuminuria
* A strip employing antibody-enzyme
conjugate that binds the albumin
* PRINCIPLE: enzyme immunoassay
* REAGENTS:
* Gold-labeled antibody
* ß-galactosidase
* Chlorophenol red galactoside
MICRAL TEST
92
MICRAL TEST PRINCIPLE:
enzyme immunoassay
93
MICRAL TEST SENSITIVITY:
0-10 mg/dL
94
* Normally filtered albumin can no longer be
reabsorbed
1. Fanconi syndrome
2. Toxic agents/heavy metals
3. Several viral infections
TUBULAR PROTEINURIA
94
MICRAL TEST INTERFERENCE:
Dilute urine = False negative
95
* Increased protein in the urine caused by
inflammation/infections that add protein in
the urine after its formation
1. Lower UTI/inflammation
2. Injury / trauma
3. Menstrual Contamination
4. Prostatic fluid / spermatozoa
5. Vaginal Secretion
POST-RENAL PROTEINURIA(“after”)
96
REAGENT STRIP FOR PROTEIN(60 SECONDS)
PRINCIPLE:
Based on the protein error-of-indicator principle.
97
* At a constant pH, the development of any green color is due to the presence of protein.
* The reaction is extremely sensitive to albumin (as it contains the most amino groups), but is much less sensitive to globulins.
REAGENT STRIP FOR PROTEIN(60 SECONDS)
PRINCIPLE: Based on the protein error-of-indicator principle.
98
PROTEIN REAGENTS
MULTISTIX:
Tetrabromphenol blue
99
PROTEIN REAGENTS
CHEMSTRIP:
Tetrachlorophenol
Tetrabromosulfonphthalein -(indicator used)
100
PROTEIN FALSE-POSITIVE:
✓ Highly buffered alkaline urine
✓ Pigmented specimen
✓ Phenazopyridine
✓ Quarternary ammonium compound
(detergents)
✓ Antiseptics
✓ Chlorhexidine
✓ Loss of buffer from prolonged exposure
of the reagent strip to the specimen
✓ High specific gravity
101
PROTEIN FALSE-NEGATIVE:
Proteins other than albumin,
microalbumin
102
A cold precipitation test that reacts equally with all forms of proteins
SULFOSALICYLIC ACID (SSA) PRECIPITATION
103
SULFOSALICYLIC ACID (SSA) PRECIPITATION
False positives:
- Contrast media
- Antibiotics in high concentration (penicillin, cephalosporin )
-Uncentrifuged turbid urines can look positive.
- SSA should always be performed on urine supernatant
104
SULFOSALICYLIC ACID (SSA) PRECIPITATION
False negatives:
- buffered alkaline urine
- Dilute urine
- Turbid urine - may mask a positive reaction.
105
* reabsorption of sodium and the tubular secretion of hydrogen and ammonium ions
* excrete non-volatile acids produced by normal body metabolism
KIDNEYS
105
regulate the acid-base balance
of the body
KIDNEYS & LUNGS
106
Important in the identification of crystals and
determination of unsatisfactory specimens
pH
106
NORMAL pH
random:
4.8-8.0
107
NORMAL pH
1st morning:
5.0-6.0
108
pH of 9.0
UNPRESERVED URINE
109
CAUSES OF ACIDIC URINE:
* diabetic mellitus
* starvation
* high protein diet
* cranberry juice
* emphysema, dehydrtion, diarrhea, presence of acid producing bacteria (E. coli), medications
110
CAUSES OF ALKALINE URINE:
* renal tubular acidosis
* vegetarian diet
* after meal
* vomiting
* old specime, hyperventilation, presence of urease-producing bacteria
111
pH CLINICAL SIGNIFICANCE:
* Respiratory or metabolic alkalosis
* Defects in renal tubular secretion and reabsorption of
acids and bases – renal tubular acidosis
* Renal calculi formation and prevention
* Treatment of urinary tract infections
* Precipitation/ identification of crystals
* Determination of unsatisfactory specimen
112
If kept for any length of time fo pH , it should be _____
refrigerated
113
An accurate measurement of pH is done on a_____
freshly voided specimen
113
pH During sleep:
decreased pulmonary ventilation causes Respiratory acidosis-thus, a first waking urine is highly acidic.
114
Urine pH is an important screening test for the diagnosis of_____
renal disease, respiratory disease,
and certain metabolic disorders
115
If urine pH is to be useful, it is necessary to use pH information in comparison with other
diagnostic information.
TRUE
116
REAGENT STRIP FOR Ph (60 SECONDS)
PRINCIPLE:
Based on the “DOUBLE INDICATOR SYSTEM”
117
REAGENT STRIP FOR Ph (60 SECONDS)
REAGENTS:
Methyl red and Bromthymol Blue
118
REAGENT STRIP FOR Ph (60 SECONDS)
INTERFERENCES:
Run-over from adjacent pads
Old specimens
119
clear red urine
HEMOGLOBINURIA
120
cloudy red urine
HEMATURIA
121
clear red (reddish-brown) urine
MYOGLUBINURIA
122
HEMATURIA SEEN IN:
* glomerulonephritis
* renal calculi, tumors
* strenous exercise, trauma
* MICROSCOPIC: intact RBC
123
HEMOGLOBINURIA SEEN IN:
* intravascular hemolysis
* transfusion reactions
* hemolytic anemia
* severe burns
* HEMOGLOBIN - product of RBC destruction, releasing hemoglobin
124
MYOGLOBINURIA SEEN IN:
* rhabdomyolysis
* muscular injury, crush syndrome
* extensive exertion
* Heme portion of the myoglobin is toxic to the renal tubules
125
REAGENTSTRIPFOR BLOOD(60 SECONDS)
PRINCIPLE:
“ Pseudoperoxidase activity of
Hemoglobin
126
Based on the liberation of oxygen from peroxidelike activity of heme from free hemoglobin.
REAGENTSTRIPFOR BLOOD(60 SECONDS)
PRINCIPLE: “ Pseudoperoxidase activity of
Hemoglobin”
126
REAGENTSTRIPFOR BLOOD(60 SECONDS)
PRINCIPLE: “ Pseudoperoxidase activity of
Hemoglobin” REAGENTS
CHEMSTRIP:
dimethyldihydroperoxyhexane and tetramethylbenzidine
127
REAGENTSTRIPFOR BLOOD(60 SECONDS)
PRINCIPLE: “ Pseudoperoxidase activity of
Hemoglobin” REAGENTS
MULTISTIX:
Diisopropylbenzene dihydroperoxide and 3,3’,5,5’ – tetramethylbenzidine
128
BLOOD
FALSE-POSITIVE:
✓ Strong oxidizing agents
✓ Bacterial peroxidases
✓ Menstrual contamination
129
BLOOD
FALSE-NEGATIVE:
✓ High specific gravity/ crenated cells
✓ Formalin
✓ Captopril
✓ High concentration of nitrite
✓ Ascorbic acid greater than 25 mg/dL
✓ Unmixed specimens
130
* A bile pigment produced from bilirubin when
bacteria act on it in the intestine.
* It is a colorless substance.
* It is oxidized to urobilin(stercobilin) responsible for the brown color of stool
UROBILINOGEN
131
UROBILINOGEN NORMAL VALUE =
< 1 mg/dL or Ehrlich unit
132
UROBILINOGEN SPECIMEN:
Afternoon urine (2-4pm)
133
REAGENT STRIP FOR UROBILINOGEN (60SECONDS)
PRINCIPLE:
“Ehrlichs Reaction”
134
REAGENT STRIP FOR UROBILINOGEN (60
SECONDS)
PRINCIPLE: “Ehrlichs Reaction” REAGENT
MULTISTIX:
p-diethylaminobenzaldehyde (PDAB or Ehrlich Reage
135
REAGENT STRIP FOR UROBILINOGEN (60
SECONDS)
PRINCIPLE: “Ehrlichs Reaction” REAGENT
CHEMSTRIP:
4- methoxybenzene diazoniumtetrafluoroborate (specific for urobilinogen)
136
UROBILINOGEN
FALSE-POSITIVE:
✓ porphobilinogen
✓ Indican
✓ p-aminosalicylic acid
✓ sulfonamides
✓ Methyldopa
137
UROBILINOGEN
FALSE-NEGATIVE:
✓ Old specimens
✓ Preservation in formalin
✓ High conc. of nitrite
138
✓ Differentiate urobilinogen, porphobilinogen and other Ehrlich-reactive compounds
✓ Uses extraction with organic solvents: Chloroform and Butanol
WATSON-SCHWARTS
139
Rapid screening test for porphobilinogen (>2mg/dL)
HOESCH TEST(INVERSE EHRLICH REACTION)
140
Rapid screening tests for UTI/Bacteria
NITRITE
141
NITRITE SPECIMEN:
1st morning or 4-hour urine
142
Most species of bacteria in the urine cause
nitrates, which are derived from dietary
metabolites, to be converted to nitrites
NITRITE
143
A negative nitrite test does not necessarily mean that the urine is free of all bacteria, particularly if there are clinical symptoms, because some bacteria do not produce nitrites.
TRUE
144
NITRITE CLINICAL SIGNIFICANCE:
* CYSTITIS
* PYELONEPHRITIS
* Evaluation of antibiotic therapy
* Monitoring of patients at high risk for UTI
* Screening of urine culture specimens
145
REAGENT STRIP FOR NITRITE(60 SECONDS)
PRINCIPLE:
Based on “ Greiss Reaction”
146
REAGENT STRIP FOR NITRITE(60 SECONDS)
PRINCIPLE: Based on “ Greiss Reaction” REAGENT
MULTISTIX:
p-arsalinic acid, tetrahydrobenzo (h)- quinoline-3-ol
147
REAGENT STRIP FOR NITRITE(60 SECONDS)
PRINCIPLE: Based on “ Greiss Reaction”
CHEMSTRIP:
Sulfanilamide, hydroxytetrahydro
benzoquinoline
* NITRITE
148
NITRITE FALSE-POSITIVE:
✓ Improperly preserved
specimens
✓ Highly pigmented urine
149
NITRITE FALSE-NEGATIVE:
✓ Nonreductase-containing bacteria
✓ Insufficient contact time of
bacteria and urinary nitrate
✓ Lack of urinary nitrate
✓ Large quantities of bacteria
converting nitrite to nitrogen
✓ Presence of antibiotics
✓ High concentration of ascorbic acid
150
* White cells in the urine usually indicate a urinary tract infection.
* The leukocyte esterase (LE) test detects esterase, an enzyme released by white blood cells. Positive test results are clinically significant
* The combination of the LE test with the urinary nitrite test -an excellent screen for predicting a urinary tract infection.
* A urine sample that tests positive for both nitrate and leukocyte esterase should be cultured for pathogenic microorganisms
* The urinary nitrite and LE tests- to screen patients at high-risk for urinary tract infections: pregnant women, school-age females, elderly patients, and persons with
a history of urinary tract infections
LEUKOCYTE ESTERASE
151
# ```
REAGENT STRIP FOR LEUKOCYTES (120 SECONDS)
PRINCIPLE:
Based on “Leukocyte Esterase”
152
REAGENT STRIP FOR LEUKOCYTES (120
SECONDS)
PRINCIPLE: Based on “Leukocyte Esterase”
MULTISTIX:
Derivatized pyrrole amino acid ester, diazonium salt
153
REAGENT STRIP FOR LEUKOCYTES (120
SECONDS)
PRINCIPLE: Based on “Leukocyte Esterase”
CHEMSTRIP:
Indoxylcarbonic acid ester, diazonium salt
154
LEUKOCYTE ESTERASE
FALSE-POSITIVE:
✓ Strong oxidizing agents
✓ Formalin
✓ Highly pigmented urine
✓ Nitrofurantoin
155
LEUKOCYTE ESTERASE
FALSE-NEGATIVE:
✓ High concentrations of protein
✓ Glucose
✓ Oxalic acid
✓ ascorbic acid
✓ gentamicin,
✓ Cephalosporins
✓ Tetracycline
✓ Inaccurate timing
