CHEMICAL EXAMINATION OF URINE Flashcards
1
Q
Bacterial decomposition, urinary tract
infection
A
Foul-ammonia like
2
Q
Ketones (diabetes mellitus,
starvation, vomiting)
A
Fruity, sweet
3
Q
Tyrosinemia
A
rancid
4
Q
Isovaleric acidemia
A
sweaty feet
5
Q
Methionine malabsorption
A
Cabbage
6
Q
Contamination
A
Bleach
7
Q
”Galunggong-like Odor”
Trimethylaminuria
A
rotting fresh
8
Q
Phenylketonuria
A
mousy
9
Q
Principle: Double Indicator System
A
pH
10
Q
Principle: Protein Error of Indicator
A
protein
11
Q
Principle: Double-Sequential Enzymatic
Reaction
A
glucose
12
Q
Principle: Nitroprusside Reaction
A
ketones
13
Q
Principle: Pseudoperoxidase Activity of
Hemoglobin
A
blood
14
Q
Intact RBC: “Speckled-Pattern” upon
contact in pad
A
blood
15
Q
Principle: Diazo Reagent
A
bilirubin
16
Q
Principle: Ehrlich’s Reaction (Multistix)
Principle: Diazo Reaction (Chemstrip)
A
urobilinogen
17
Q
Principle: Greiss Reaction
A
nitrite
18
Q
Principle: Hydrolysis of Ester
WBCs
A
leukocyte esterase
19
Q
Principle: Change in pKa of
Polyelectrolytes
A
specific gravity
20
Q
Principle: Action of ________ to
reduce a dye in the impregnated pad
A
Ascorbic Acid
21
Q
parameter pH: Red ⟶ Yellow
A
Methyl Red (pH 4-6)
22
Q
parameter pH: Yellow ⟶ Green ⟶ Blue
A
Bromothymol Blue (pH 6-9)
23
Q
No chemical interference, but bacterial overgrowth may falsely elevate pH
A
TRUE
24
Q
Principle: Protein Error of Indicators (color change without pH change)
A
protein
25
indicators of protein
Tetrabromophenol blue (Multistix)
Tetrachlorophenoltetrabromosulfonphthalein
(Chemstrip)
26
false positives of protein
1. highly alkaline urine
2. detergents
3. blood contamination
4. pigmented urine
27
Low albumin (as strips mainly detected albumin)
false negatives
28
Semiquantitative Reagent Strip Methods
● Developed to monitor renal disease using random
or first morning urine specimens.
● Based on immunochemical assays or
albumin-specific reagent strips with creatinine
measurement (A:C ratio).
microalbuminuria testing
29
Uses gold-labeled anti-human albumin
antibody-enzyme conjugate.
■ Albumin binds to antibody, producing color change
(white to red).
■ Read visually after 1 minute.
■ Results: 0-10mg/dL.
Micral-Test (Roche Diagnostics)
30
Uses immunochromographic technique with
blue latex particles.
ImmunoDip (Sekisui Diagnostics
31
(Negative, darker
bottom band)
<1.2 mg/dl
32
(Borderline, equal
bands).
1.2-1.8 mg/dl
33
(Positive, darker top
band)
2.0-8.0 mg/dL.
34
Specific for glucose using a double enzyme reaction
GLUCOSE OXIDASE TEST
35
Glucose oxidase reacts with glucose +
02- Gluconic acid + H202.
○ Peroxidase reacts with H202 + chromogen → Color change proportional to glucose concentration.
GLUCOSE OXIDASE TEST
36
Chromogens used in glucose:
■ Multistix:
potassium iodide (green to brown)
37
Chromogens used in GLUCOSE
■ chemstrip:
Tetramethylbenzidine (Yellow to green).
38
False Positives in glucose
contaminated containers (peroxidase, oxidizing detergents)
39
False Negatives in glucose
High levels of ascorbic acid (Vitamin C)
■ High ketones (affect low glucose concentrations).
■ High specific gravity & low temperature
■ Bacterial degradation (if urine is left unpreserved at room temp
40
Non-specific test for reducing substances (glucose,
galactose, lactose, fructose, maltose, pentose)
copper reduction test
41
Based on Benedict's principle:
■ CuSO4 (blue) + Reducing sugar + Heat
Cu2O(Orange/Red)
copper reduction test (clinitest)
42
Contains OuSO4, Na2003, NaOH,Na citrate.
○Generates heat for reaction.
clinitest tablet reaction
43
Pass-through effect: High glucose levels turn
orange-red, then revert to green-brown, leading to
false-negative interpretation.
TRUE
44
________ minimizes pass- through (detects
up to 5 g/ dL. glucose).
*Two-drop method
45
Not confirmatory for glucose (minimumsensitivity 200 mg/dL).
clinitest tablet reactioj
46
Interfering substances:
galactose
lactose
ascorbic acid
drug metabolites
47
Uses sodium nitroprusside (nitroferricyanide) reaction in an alkaline medium:
KETONES
48
Detects acetoaœetic acid and acetone (with glycine)
○ ß-hydroxybutyrate is not directly measured
○ Results appear as a ______
KETONES; PURPLE
49
False Positives in ketones:
Large amounts of levodopa
sulfhydryl-containing
drugs (e.g, MESNA, captopril)
50
Improper preservation leading to volatilization of
acetone and breakdown of acetoacetic acid by
bacteria
false negative in ketones
51
Used as a confirmatory test for ketones in urine,
serum, and other bodily fluids
acetest tablet test
52
Contains sodium nitroprusside, glycine, disodium
phosphate, and lactose
acetest tablet test
sodium nitroprusside
glycine
disodium phosphate
lactose
53
BLOOD: Uses pseudoperoxidase activity of hemoglobin to
oxidize
tetramethylbenzidine = green-blue color
54
False-Positives in blood
■ Menstrual contamination.
■ Strong oxidizing agents (eg, bleach).
■ Bacterial enzymes (eg., E. coli peroxidase)
55
High vitamin C (ascorbic acid) levels.
High specific gravity preventing RBC lysis.
Formalin preservative or hypertension medication
(captopril).
High nitrite concentration (> 10 mg/dL).
Improper specimen mixing leading to settled RBCs
at the bottom.
FALSE NEGATIVES
56
Reagent Strip (Diazo) Reactions
■ Principle: Uses diazo reaction
BILIRUBIN
57
Color indicator in bilirubin
■ Negative →
light tan/yellow
58
Beige/Pink
small
59
Dark Pink
moderate
60
Violet/Purple
large
61
Phenazopyridine compounds (orange urine
pigmentation).
■ Indican, Lodine metabolites.
false positive in BILIRUBIN
62
Exposure to light (bilirubin breaks down into
biliverdin, which does not react).
■ High ascorbic acid (Vitamin C) & nitrite levels -
interfere by binding to diazonium salts
false negative in bilirubin
63
More sensitive than reagent strips (detects 0.05-0.1
mg/dL bilirubin).
○ Uses p-nitrobenzenediazonium-p-toluenesulfonate on
a special mat.
ICTOTEST = CONFIRMATORY OF BILIRUBIN
p-nitrobenzenediazonium-p-toluenesulfonate
64
Positive result: Blue to purple color on the mat.
■ If interference occurs, ______ helps remove
interfering substances.
ictotest (confirmatory test)
adding water
65
Multistix (Ehrlich reaction)
UROBILINOGEN = PDAB
66
Chemstrip (Diazo reaction - more specific)
UROBILINOGEN - 4 methoxybenzene-diazonium-tetraflurporiborate = red azo dye
67
Color change: Light pink → Dark pink in uribilinogen
ehrlich reagent
68
Color change: White → Pink in urobilinogen
diazo reaction
69
False Positives (Ehrlich reaction on Multistix):
○ Ehrlich-reactive compounds
■ Porphobilinogen
■ Indican
■ p-aminosalicylic acid
■ sulfonamides
■ methyldopa
■ procaine
■ chlorpromazine.
70
is clinically significant but
reagent strip is not a reliable screening method.
porphobilinogen presence
71
Higher temperatures ______ Ehrlich reaction
sensitivity.
increase
72
○ Photo-oxidation to urobilin (improper specimen
preservation).
○ High nitrite concentrations interfere with Chemstrip
azo-coupling reaction.
○ Formalin preservatives can also lead to
false-negative results.
false negative in urobilinogen
73
Higher urobilinogen levels after meals due to ______
bile salt excretion.
increased
74
Detects nitrite, which is normally absent in urine.
○ _____ bacteria reduce nitrate
Gram-negative
75
Step 1: Nitrite reacts with aromatic amine
(para-arsanilic acid or sulfanamide) → Diazonium
salt.
Step 2: Diazonium salt reacts with
tetrahydrobenzoquinolin Pina azo dye
○ Color change: Any shade of pink = Clinically
significant.
Chemical reaction (Greiss reaction): nitrite
76
Non-nitrate reducing bacteria
Insufficient urine retention time in bladder
Low dietary nitrate intake
Overgrowth of bacteria reducing nitrite to nitrogen
Interference by antibiotics and ascorbic acid
FALSE NEGATIVE NITIRTE
77
Bacteria need _____ in the bladder to
produce nitrite
● Use the ____ specimen for accuracy.
>4 hours
first morning urine for nitrite
78
■ External contamination of urine.
■ Urine left standing at room temperature, Allowing
bacterial growth.
false positive for nitrite
79
■ External contamination of urine.
■ Urine left standing at room temperature, Allowing
bacterial growth.
false positive for nitrite
80
hydrolyzes an acid ester on the reagent pad
Produces aromatic compound & acid.
○ Aromatic compound reacts with diazonium salt → Forms purple azo dye.
○ Longest reagent strip reaction time:
leukocyte esterase
2 mins
81
■ Strong oxidizing agents (bleach, formalin) in
container.
■ Highly pigmented urine & nitrofurantoin
(antibiotic) may obscure results.
false positive for leukocyte esterase
82
High concentrations of:
●
Protein (>500 mg/dL)
●Glucose (>3 g/dL)
● Oxalic Acid
● Ascorbic Acid (Vitamin C).
● Ascorbic Acid interferes with Diazonium salt
reaction.
● Crenated WBCs in high specific gravity urine →
Prevents esterase release.
■ Certain antibiotics (gentamicin, cephalexin,
cephalothin, tetracycline) reduce sensitivity.
false negative for leukocyte esterase
83
Polyelectrolyte ionizes→Releases hydrogen ions (H⁺)
in proportion to urine ion concentration.
○ More concentrated urine →More H⁺ released →Lower
pH.
specific gravity
84
indicator detects pH change: Blue
(alkaline, 1.000) →Green →Yellow (acidic, 1.030).
bromothymol blue
85
Readings are taken in _____ increments using a color chart.
0.005
86
High protein concentration→Slightly _____ SG due
to protein anions.
increases
87
Alkaline urine (pH≥ 6.5) → ____ SG readings due
to bromothymol blue interference.
Decreases
88
Correction: Add 0.005 to SG readings when pH is ____
or higher (automated readers adjust for this).
6.5
89
Additional Parameters: URS-14
○Ascorbic Acid
○ Calcium
○ Creatinine
○ Micro-Albumin
90
reduction of a colored
indicator by ascorbic acid. _________ acts as a
strong reducing agent, decolorizing the reagent pad.
ascorbic acid
91
______– a redox
indicator that changes color from blue to colorless
when reduced by ascorbic acid
2,6-Dichlorophenol-indophenol(DCPIP)
92
complex metric reaction, where
calcium ions react with a chromogenic reagent to form
a colored complex, indicating the concentration of
calcium in urine.
CALCIUM = COMPLEX METRIC
93
Calcium reacts with o-cresolphthalein in
an alkaline environment, forming a purple-colored
complex.
CPC METHOD = ALKALINE
94
Formsablue-violet complex in
acidic conditions with high specificity for calcium.
arsenazo III = ACIDIC
95
The test is based on the peroxidase-like activity of
creatinine in an alkaline environment, where it reacts
with a creatinine-specific chromogen to produce a
color change proportional to the creatinine
concentration.
creatinine = ALKALINE
96
forms a red-orange color in
an alkaline environment when creatinine reacts with
picric acid.
3,5 dinitrobenzoic acid or jaffe reaction
97
uses a dye-binding method where albumin
binds to a specific dye, leading to a color change that
correlates with albumin concentration in urine.
microalbumin
98
binds
to albumin and produces a color change from yellow
to green or blue, depending on the albumin
concentration.
tetrabromophenol blue or bromocresol green
99
binds
to albumin and produces a color change from yellow
to green or blue, depending on the albumin
concentration.
tetrabromophenol blue or bromocresol green
