CHEMICAL EXAMINATION OF URINE
Reagent Strip


Simple, rapid means for performing medically
significant chemical analysis of urine
10 basic parameters:
o Glucose – 30 secs.
o Bilirubin – 30 secs.
o Ketones – 45 secs.
o Specific gravity – 45 secs.
o Blood – 60 secs.
o pH – 60 secs.
o Protein – 60 secs.
o Urobilinogen – 60 secs.
o Nitrite – 60 secs.
o Leukocyte – 120 secs.

11th parameter Ascorbic Acid – causes false
negative result

False Negative in the presence of Ascorbic Acid:
BBLNGBlood, Bilirubin, Leukocyte Esterase,
Nitrite and Glucose

4 basic parameters: pH, specific gravity, protein,
glucose

2 major types of reagent strips (trade names):
1. Multistix (Siemens)
2. Chemstrip (Roche)

Chemical-impregnated absorbent pads attaché
to a plastic strip
Color- producing chemical reaction


Interpreted by comparing the color produced on
the pad with a chart supplied by the
manufacturer.

Semiquantitative value
 trace, 1+, 2+, 3+ or 4+
Reagent Strip Technique
 Dip the reagent strip briefly into a well-mixed
uncentrifuged urine specimen at room
temperature.
 Remove excess urine by touching the edge of the
strip to the container as the strip is withdrawn.
 Blot the edge of the strip on a disposable
absorbent pad.
 Wait the specified amount of time for the reaction
to occur.
 Compare the color reaction of the strip pads to the
manufacturer’s color chart in good lightning.
Care of Reagent Strip

Store with desiccant in an opaque, tightly closed
container.
Store below 30ᵒC; do not freeze.
Do not expose to volatile fumes.
Do not use past the expiration date.
Do not use if chemical pads become discolored.
Remove strips immediately prior to use.





Quality Control of Reagent Strip
 Test open bottles of reagent strips with known
positive and negative controls every 24 hours.
 Resolve control results that are out of range by
further testing.
 Test reagents used in backup tests with positive
and negative controls.
 Perform positive and negative controls on newly
opened bottles of reagent strips.
 Record all control results and reagent lot
numbers.
pH




Lungs and kidney
Major regulator of acid-base content of
the body
HCO3–
Reabsorbed in CT
pH 5.0-6.0
First morning urine (healthy individuals)
4.5 – 8.0
Normal random sample
Causes of Acidic and Alkaline Urine
Acidic Urine
1. Emphysema
2. Diabetes Mellitus
3. Dehydration
4. Diarrhea
5. Starvation
6. Cranberry juice
7. High-protein diet
8. Presence of acidproducing bacteria
(Escherichia coli)
9. Medications
(methenaminemandelate
[mandelamine],
fosfomycintromethamine)
Alkaline Urine
1. Hyperventilation
2. Presence of ureaseproducing bacteria
3. Renal tubular acidosis
4. Old specimens
5. Vomiting
6. Vegetarian diet
Clinical Significance (pH)
 Respiratory or metabolic acidosis / ketosis
 Respiratory or metabolic alkalosis
 Defects in renal tubular secretion and
reabsorption of acids and bases – renal tubular
acidosis
 Renal calculi formation
 Treatment of urinary tract infections
 Precipitation / identification of crystals
 Determination of unsatisfactory specimens
I. Pre-renal Proteinuria
Caused by the condition affecting the
plasma prior to reaching the kidney
Not indicative of actual renal disease
Frequently transient:
o Hemoglobin
o Myoglobin
o Acute phase reactant due to
inflammation
Not usually discovered in routine urinalysis
Reagent Strip Reaction (pH)
 Measures pH between 5 – 9
 Principle:

DOUBLE-INDICATOR SYSTEM OF METHYL
RED AND BROMTHYMOL BLUE
Bence Jones Protein
 Seen in case of multiple myeloma
 Monoclonal immunoglobulin light chain
pH range 4 - 6



pH range 6 - 9


pH 5  orange; pH 9  green
No known substance to cause interference of pH
test
Prevent runover between pH and CHON  false
acidic reading
PROTEIN (ALBUMIN)




Most indicative of renal disease
Proteinuria  early renal disease
Normal value: <10 mg/dL or 100mg/24h (usually
albumin)
Other CHON:
o Tubular microglobulins, Tamm-Horsfall
protein (uromodulin) produced by the
tubules, and proteins from prostatic,
seminal, and vaginal secretions
Clinical Significance (Protein)
Proteinuria
 Does not always signify renal disease
 Presence requires additional testing
 Clinical proteinuria  ≥ 30 mg/dL or 300 mg/L
 3 major categories:
o Pre-renal
o Renal
o Post-renal
II.
Screening Test: Solubility test
o Coagulates at 40-60ᵒC (turbid);
dissolves when attempt reaches 100ᵒC
(clear)
o Filter 100ᵒ C and observe for turbidity as
it cools to 40-60ᵒC
Confirmatory: Serum electrophoresis / IE
Renal Proteinuria
True renal disease (glomerular/tubular
disease)
1. Glomerular Proteinuria
 Selective filtration is impaired
 Increased protein, RBCs, WBCs
 Causes:
o
Amyloid material
o
Toxic substances
o
Immune complexes found in
lupus erythematous and
streptococcal glomerulonephritis
o
Strenuous exercise
o
Dehydration
o
Associated with hypertension preeclampsia
2. Tubular Proteinuria
 Disorders affecting tubular reabsorption
 Filtered albumin can no longer be
reabsorbed
 Causes:
o
Exposure to toxic substances and
heavy substances
o
Severe viral infections
o
Fanconi syndrome

Benign Proteinuria: Transient
o
Strenuous exercise
o
High fever
o
Dehydration
Exposure to cold
3. Orthostatic (Postural) Proteinuria
 Seen frequently in young adults
 Appears in vertical position; disappears
in horizontal position
 Empty bladder before going to bed,
collect first morning upon rising
 Collect second specimen after
remaining in vertical position for several
hours
 Results:
o
Negative (-)  1st sample
o
Positive (+)  2nd sample
o
4. Microalbuminuria
 Diabetic nephropathy leading to
reduced glomerular filtration and
eventual renal failure
 Prevented through better stabilization
of blood glucose levels and controlling
of hypertension
 24-hour urine sample
 Positive (+): Microalbumin is significant
o
30-300 mg/24hr
o
20-200 ug/min
III.
Post-renal Proteinuria
Protein can be added to a urine specimen as
it passes through the structures of the
lower urinary tract (ureters, bladder,
urethra, prostate, and vagina)
Bacterial and fungal infections ad
inflammations
The presence of blood as the result of injury
or menstrual contamination
Presence of prostatic fluid and large
amounts of spermatozoa
Reagent Strip (Protein)
 Principle:

PROTEIN ERROR OF INDICATORS
Chemstrip: 6 mg/dL albumin
Interference (Protein)

False-Positive
 Highly buffered alkaline
urine
 Pigmented specimens,
phenazopyridine
 Quaternary ammonium
compounds (detergents)
 Antiseptics,
chlorhexidine
 Loss of buffer from
prolonged exposure of
the reagent strip to the
specimen
 High specific gravity

Reagent:

Multistix: Tetrabromphennol blue

Chemstrip: 3’,3”,5’,5” tetrachlorophenol 3,4,5,6 tetrabromosulfophthalein
Sensitivity:

Multistix: 15-30 mg/dL albumin
 Proteins other than
albumin
 Microalbuminuria
Correlations with other tests (Protein)

Blood

Nitrite

Leukocytes

Microscopic
Other Albumin Qualitative Test
General Principle:
Precipitation of protein by heat and coagulation
by chemical reagents
Test
Heat and Acetic
acid
Sulfosalicylic
Acid (SSA) /
Exton’s Test
Heller’s Ring
Test
Purdy’s Test
Picric Acid Test
Robert’s Ring
Test

False-Negative
Potassium
Ferrocyanide
Test
Reagent
Acetic Acid
Sulfosalicylic Acid
or Sodium Sulfate
Concentrated
Nitric Acid
50% Acetic Acid
Saturated
solution of picric
acid
Magnesium
sulfate or
concentrated
nitric acid
Glacial acetic acid
and K
ferrocyanide
Results
White
cloudiness
White ring at
zone of contact
White opaque
ring
White
cloudiness
Precipitation
White ring at
zone of contact
Cloudiness
(proteases)
Test
Esbach’s Test
Shevky and
Stafford Test
Kingsbury
Clark Test
Kwilecki’s
Test
Purdy’s Test
Reagent
Picric acid and
Citric acid
Tsuchiya’
3% SSA
10% Ferric chloride
Results
GLUCOS

PRECIPITATION


Grams/24 hr or
mg/dL

Specimen:
24-hours urine
50% Acetic acid
10% K ferrocyanide
Most frequent chemical analysis performed on
urine
Value: detection and monitoring of DM
Most informative glucose results are obtained
from specimens collected under controlled
conditions
Fasting or 2-hour after meal specimen
o Advised empty bladder then collect 2nd
specimen
Clinical Significance (Glucose)
Diabetes Mellitus Hyperglycemia
Glycosuria Tubular transport of glucose ceases
 180 mg/dL
Microalbumin Testing
Immunologic Tests
Micral-Test
Gold-labeled
antibody,
-galactosidase,
Principle:
Enzyme
Chlorophenol red
Immunoassay
galactoside
Immunodip
Principle:
Immunochromographics
Antibody-coated
blue latex
particles
Sensitivity:
0 – 10 mg/dL
Interference:
False negative
 dilute urine
Sensitiviy:
1.2 – 8.0 mg/dL
Interference:
False negative
 dilute urine
Albumin:Creatinine Ratio
ClinitestMicroa
lbumin Strips / Albumin:
Sensitivity:
DiodoMultistix-Pro
Albumin:
dihydroxydinitro
10 – 150 mg/dL
Principle:
-phenyl
Creatinine:
Sensitive
tetrabromosulp
10 – 300 mg/dL,
albumin tests
honphthalein
0.9 -26.5 mmol/L
related to
creatinine
concentrations
to convert for
patient
hydration
Creatinine:
Copper sulfate,
tetramethylbenzidine and
diisopropyl
benzene
dihyroperoxide
Interference:
Visibly bloody
or abnormally
colored urine
Creatinine:
Cimetidine: False
positive
Hyperglycemia-Associated
Renal – Associated
 Fanconi syndrome
 Diabetes Mellitus
 Advanced renal disease
 Pancreatitis
 Osteomalacia
 Pancreatic cancer
 Pregnancy
 Acromegaly
 Cushing syndrome
 Hyperthyroidism
 Pheochromocytoma
 CNS damge
 Stress
 Gestational diabetes
 Gestational diabetes - hyperglycemia that occurs
during pregnancy and disappears after delivery
Reagent Strip Reactions (Glucose Oxidase)
 Mixture of glucose oxidase, peroxidase,
chromogen and buffer

Principle:

DOUBLE SEQUENTIAL ENZYME REACTION

Reagents:

Multistix: Glucose oxidase & Peroxidase
Potassium iodide (green & brown)

Chemstrip: Glucose oxidase & Peroxidase
Tetramethybenzidine (yellow to green)
 Sensitivity:


Multistix: 75 – 125 mg/dL
Chemstrip:40 mg/dL
Interference(Glucose Oxidase)
False-Positive
 Contamination by
oxidizing agents and
detergents
Other Sugars:
False-Negative
 High levels of ascorbic
acid
 High levels of ketones
 High specific gravity
 Low temperature
 Improperly preserved
specimens
Copper Reduction Test (Clinitest)
 Relies to the ability of glucose and other
substances to reduce copper sulfate to cuprous
oxide in the presence of alkali and heat.
Sugar
Fructose:
 Fructokinase
deficiency
Pentose:
 Genetic
disorder
 Xylitol
 Dehydrogenase
deficiency
Other Glucose Qualitative Test
General Principle: Reduction Principle
Test
Benedict’s
Test
Clinitest
Tablet
Fehling’s Test
a.Fehling’s A
b.Fehling’s B
Osazone Test
(phenylhydrazine)
Nylander’s
Test
Moore
Heller’s
Reagent
CuSO4 / Sodium
Citrate (buffer) /
NaCO3
CuSO4 / Sodium
Citrate / NaCO3/
NaOH
Positive Results
(-): Blue
±: Green, no ppt.
1+: Green with ppt.
2+: Yellow-green
w/ ppt.
3+: Muddy-orange w/
yellow ppt.
4+: Orange to brick
red
Range of Colors
(blue to orange/red)
Lactose:
 Lactokinase
deficiency
 Seen in
lactating
women and
long term milk
diet
Galactose:
 Inborn error of
metabolism
Yellow ppt.
Cupric salt/dH2O
Rochelle Salt/
KOH/ dH2O
Phenylhydrazine
HCl
Sodium acetate
Bismuth
subnitrite
10% KOH
Bright yellow needle
crystal
Brown – black solution
1% or less: canary
yellow
1-2%: wine yellow
2-3%: cherry red
3-4%: rum
>4% : dark brown-black
Maltose:
Test
Sellwanoff’s Test
Result
Borchardt’s Test
(Resorcinol an
HCl)
Red solution /
red ppt.
Barfoed’s Test
Black hue
Bial’s Test
Cole Test (FeCl3
and charcoal)
Green color
Tauber’s Test
(Benzidine and
glacial HAc)
Pink-cherry red
Tollen’s Test
(conc. HCl and
phloroglucin)
Purple
Rubner’s Test
(Lead acetate
and conc.
NH4OH)
Red Color
Ormsby Test
(methylamine
HCl and NaOH)
Mucin acid test
(Conc. HNO3)
White Color
Mucin acid test
(Conc. HNO3)
White ppt.
Tollen’s Test
(Conc. HCl and
phloroglucin)
Purple ppt.
Osazone Test
Yellow needle
crystals
Red Color
Barfoed’s Test
Other Test for Ketones
KETONES

Intermediate products of fat metabolism
o Acetone (2%)
Water soluble
Non-reversible spontaneous
decarboxylation product of diacetic
acid
o Acetoacetic acid (20%)
Diacetic acid
Most abundant in urine
o Beta-hydroxybutyric acid (78%)
Reversible to diacetic acid
Clinical Significance (Ketones)
 Diabetic ketoacidosis (IDDM)
 Insulin dosage monitoring
 Starvation
 Excessive carbohydrate loss
Reagent Strip (Ketones)
 Principle:

Based on SODIUM NITROPRUSSIDE
(NITROFERRICYANIDE) REACTION

Beta-hydroxybutyric acid is not measured

Sensitivity:
 Multistix: 5-10 mg/dLacetoacetic acid
 Chemstrip: 9 mg/dLacetoacetic acid;
70 mg/dL acetone
Interference (Ketones)
False-Positive
 Phthalein dyes
 Highly pigmented red
urine
 Levodopa
 Medications
containing free
sulfhydryl groups
False-Negative
 Improperly preserved
specimens
Test
Acetest tablet
Rothera’s Tube
Test
TESTS FOR ACETONE
Reagents
Na Nitroprusside/
Glycine/ Disodium
phosphate/Lactose
Na Nitroprusside/
Ammonium sulfate
Lileben’sIodoform
Test
Gunning’s Test
Frommer’s Test
Legal’s Test
KOH/ Iodine/ KI
Alc. Iodine solution
KOH/
salicylaldehyde
Na Nitroprusside
Results
Lavender purple
Red – purple
ring at the
zone of
contact
Yellow ppt.
of iodoform
Yellow ppt.
of iodoform
Purple ring
Violet
TESTS FOR DIACETIC ACID
Test
Reagents
Results
Gerhard’s Test FeCl3
Bordeaux red
Lindemann’s
30% Acetic acid/
Reddish violet
Iodine and
Test
chloroform
TESTS FOR BETA-HYDROXYBUTYRIC ACID
Test
Reagents
Results
Hart’s Test
HAc / H2O2
Red ring
Ammonium
Red
Osterberg’s
Test
sodium hydroxide
BLOOD




Hematuria – intact RBC (cloudy red)
Hemoglobinuria– Clear red
> 5 cells / µL urine = clinical significant
Chemical tests for hemoglobin  most accurate
means for determining the presence of blood
Microscopic examination  differentiate
between hematuria and hemoglobinuria

Hematuria
Disorders of renal or genitourinary origin
Bleeding is the result of trauma or damage to the
origin
Major causes: Renal calculi, glomerular diseases,
tumors, trauma, pyelonephritis, exposure to toxic
chemicals and anticoagulant therapy
Cause of Hematuria
Lower UTI
Renal Calculi
Glomerular disease (LE)
Tumor
Glomerulonephritis
Trauma/ Exposure to
toxic chemicals /
Anticoagulants
Malignant papilloma
Comment
Presence of RBC, WBC and
bacteria in urine
Severe back and
abdominal pain
Result of Ag-Ab reaction
that localizes in the
kidneys
Abnormal swelling in or on
part of the body
Destroyed glomerular
tissue
Nipple-like growth on the
surface of the skin and
other organs
Hemoglobinuria
Lysis of red blood cells
Result from intravascular hemolysis
Lysis of red cells in urine
Hemosiderin– large yellow-brown granules of
denatured ferritin; the result of reabsorption of
filtered hemoglobin
use of plasma for differentiation of
Hemoglobinuria and Myoglobinuria
Cause of
Hemoglobinuria
1. Transfusion reactions
2. Hemolytic anemia
3. Severe burns
4. Infection
5. Strenuous exercise/
red blood cell trauma
6. Brown recluse spider
bites
7. Malaria
Comment
 Hemoglobinuria +
hematuria = lysis of RBC
in urine
 Hemoglobinuria alone =
intravascular hemolysis
 Amount of free
hemoglobin present
exceeds the haptoglobin
content
 Occurs only when is
filtered by the
glomerulus
 Black water fever
Myoglobinuria
Myoglobin – a heme containing protein found in
muscle tissue
Seen in rhabdomyolosis (muscle destruction)
Positive with reagent strip test for blood
Produces a clear-red brown urine
Cause of Myoglobinuria
1. Muscular trauma/
crush syndromes
2. Prolonged coma
3. Muscle-wasting
disease
4. Convulsions
5. Alcoholism/overdose
6. Drug abuse
7. Extensive exertion
8. Cholesterol-lowering
stain medications
Comment
 Atrophy involving
affected parts, such as
damage muscles and its
nerves, or lack of use
 Involuntary muscle
contraction
 Associated with
cardiomegaly
Reagent Strip (Blood)
 Principle:

PSEUDOPEROXIDASE ACTIVITY OF
HEMOGLOBIN
Chromogen: tetramethylbenzidine
Color reaction: yellow-green – blue
 Speckled pattern on pad intact RBC (lysed during
contact with the pad)


BILIRUBIN
Interference (Blood)
False-Positive
 Strong oxidizing agents
 Bacterial peroxidases
(E.coli)
 Menstrual
contamination
False-Negative
High SG/ crenated cells
Formalin
Captopril
High concentrations of
nitrite
 Ascorbic acid >25 mg/dL
 Unmixed specimens




Other Tests for Blood
Tests
Benzidine Test
- most sensitive
test in blood
Gulac’s Test
Occult Blood
Benzidine
Tablet Test
Orthotoluidine
Test
Telchman’s Test
- no color
produced
Reagents
Benzidine/
H2O2
Positive Results
Green to Blue
Glacial Acetic
acid/ H2O2 /
Gulac’s gum
solution
Benzidine/
H2O2
Green to Blue
Methyl
alcohol/
acetic acid /
peroxidase
Saline
solution/
glacial HAc
Green to Blue
 100/mm3 =
greenish-blue
 300-500/mm3 =
deep blue for 1
minute
 1000/mm3 =
deep blue for 2
minutes
Crystallization of
hemine
Clinical Significance (Bilirubin)
1. Hepatitis
2. Cirrhosis – scarring of the liver
3. Other liver disorders
4. Biliary obstruction (gallstones, carcinoma)
Condition
Bile duct
obstruction
Liver damage
Hemolytic
disease
Urine Bilirubin
+++
Urine Urobiinogen
Normal
+ or Negative
++
+++
Reagent Strip (Bilirubin)

Principle:

DIAZO REACTION
Reagent:

Multistix: 2,4-dichloroaniline diaonium salt

Chemstrip: 2,6-dichlorobenzene diazonium
Salt
 Color reaction: Tan or pink to violet
 Sensitivity:

Multistix: 0.4 – 0.8 mg/dL bilirubin

Chemstrip: 0.5 mg/dL bilirubin

Clinical Significance (Urobilinogen)
1. Early detection of liver disease
2. Liver disorders, hepatitis, cirrhosis, carcinoma
3. Hemolytic disorders
Absence of urobilinogen in stool
 Indication of bile obstruction (pale stool)
Reagent Strips (Urobilinogen)

Multistix: EHRLICH REACTION
Interference (Bilirubin)
False-Positive
 Highly pigmented
urines(phenazopyridine)
 Indican (intestinal
disorders)
 Metabolites of Lodine
False-Negative
 Specimen exposure to
light
 Ascorbic acid >25
mg/dL
 High concentrations of
nitrite
Correlation with other test (Bilirubin)
 Urobilinogen
Ultzman’s
Test
Foam Test
Icto Test
Sensitivity:
0.05-0.10
mg/dL
Harrison
Spot
Fouchet’s
Test
Reagents
Ethanol solution of
Iodine
Concentrated HNO3
KOH/HCl
p-nitrobenzenediazonium-ptoluenesulfonate,
SSA, sodium
carbonate, and
boric acid
BaCl2 / Fouchet’s
reagent
BaCl2 / FeCl3
UROBILINOGEN
Interference (Urobilinogen)
Multistix
(Ehrlich’s
reaction)
Other Tests for Bilirubin (Bilirubin)
Tests
Smith’s
(Iodine Test)
Gmelin’s Test
 Chemstrip: DIAZO REACTION
Positive Results
Emerald-green
Green (biliverdin)
Violet (choletin)
Yellow/Red (Bili)
Blue-green
(bilicyanin)
Green
Yellow foam
Bluish-purple
Blue-green
Greenish-blue
spot
Chemstri
p
(Diazo
reaction)
False-Positive
 Porphobilinogen
 Indican
 p-aminosalicylic
acid
 Sulfonamides
 Methyldopa
 Procaine
 Chlorpromazine
 Highly
pigmented urine
 Highly
pigmented urine
False-Negative
 Old specimens
 Preservation in
formalin
 High
concentrations of
nitrite
Ehrlich Tube Test
 1 part of Ehrlich reagent + 10 part of urine
 Positive (+) : Cherry red color
Watson – Schwartz Differentation Test
Tube 1
2 mL urine
2mL chloroform
4 mL sodium acetate
Tube 2
2mL urine
2mL butanol
4mL sodium acetate
Hoesch Screening Test for Porphobilinogen






Rapid test
Hoesch Reagent: Ehrlich’s reagent dissolved in
6M HCl
2 drops urine + 2mL Hoesch Reagent
Positive(+): Red Color
Sensitivity: 2 mg/dL
Interference:
o False (+): methyldopa, indicant, highly
pigmented urine
o False (-): acidic pH
NITRIT

Watson – Schwartz Test Interpretation
Rapid screening test for the presence of urinary
tract infection (UTI)
Clinical Significance (Nitrite)
 Cystitis – inflammation of urinary bladder
 Pyelonephritis – inflammation of kidney
 Evaluation of antibiotic therapy
 Monitoring patients at high risk for UTI
 Screening of urine culture specimens
Reagent Strip (Nitrite)
 Principle:
 GREISS REACTION
 Basis of test: Ability of a certain bacteria to
reduce nitrate to nitrite
 Reporting: Positive or negative only
Interference (Nitrite)

Urobilinogen is soluble in both chloroform and
butanol, and porphobilinogen is soluble in neither.

If both urobilinogen and porphobilinogen are
present, both layers are red.

Before reporting the test as both are positive for
both substances, an additional chloroform
extraction should be performed on the red urine
(upper) layer in Tube 1 to ensure that the red color
is not due to excess urobilinogen.
False-Positive
 Improperly preserved
specimen
 Highly pigmented
specimen







False-Negative
Nonreductasecontaining bacteria
Insufficient contact
time between bacteria
and urinary nitrate
Lack urinary nitrate
Large quantities of
bacteria converting
nitrite to nitrogen
Presence of antibiotics
High concentrations of
ascorbic acid
High specific gravity
SPECIFIC GRAVITY
LEUKOCYTE ESTERASE




Detects the presence of esterase in the
granulocytic WBCs and monocyte
Detects the presence of leukocytes that have
been lysed, particularly in dilute alkaline urine,
and would not appear in the microscopic
examination
Positive LE is often accompanied by the
presence of bacteria
Leukocyturia without bacteriuria =
Trichomonas, Chlamydia, Yeast infection and
inflammation of renal tissues (interstitial
nephritis)
Reagent Strip (LE)
 Based on the action of LE to catalyze the
hydrolysis of an acid ester to produce an aromatic
compound and acid
Reagent Strip (Specific Gravity)
 Principle:
 pKa CHANGE (Dissociation constant) OF A
POLYELECTROLYTE IN AN ALKALINE
MEDIUM
 Blue (1.000) to shades of green-yellow (1.030)
 Reagent:
 Multistix: Poly (methyl vinyl ether/ maleic
anhydride) bromthymol blue
 Chemstrip: Ethyleneglycoldiaminoethylethertetraacetic acid, bromthymol blue
 Measures only ionic solutes
 Elevated protein can elevate the result
 Specimens with pH 6.5 or higher decreased
readings due to bromthymol blue indicator
interference

Corrected by adding 0.005

Automated strip readers automatically
corrects the reading
Interference (Specific Gravity)

Sensitivity:
 Multistix: 5 -15 WBC/hpf
 Chemstrip: 10 – 25 WBC/hpf
Interference (LE)
False-Positive
 Strong oxidizing
agents
 Formalin
 Highly pigmented
urine
 Nitrofurantoin
False-Negative
 High concentrations:
o Protein
o Glucose
o Oxalic acid
o Ascorbic acid
o Gentamicin
o Cephalosporins
o Tetracyclines
 Inaccurate timing
False-Positive
 High concentrations of
protein
False-Negative
 Highly alkaline urine
(greater than pH 6.5)