Chemical Examination of Urine Flashcards
The chemical analysis of urine routinely utilizes _______
Commercial reagent strips
Simple and rapid screening of urine specimens tests:
Bilirubin
Blood
Glucose
Ketones
Leukocyte esterase
Nitrite
pH
Protein
Urobilinogen
Urine chemistry using reagent strip, which can be completed within ______
2 minutes
Dipstick brands that are commonly used
Multistix (Siemens)
Chemstrip (Roche)
vChem Strips (Iris)
Aution Sticks (Arkray)
consists of an inert plastic strip onto which reagent-impregnated absorbent test pads are attached
Reagent strip
manner of reporting the results is based on the comparison of the colors on the chart and the strip which can either be:
(1) concentration (milligrams per deciliter)
(2) Small, moderate, or large
(3) plus system
(4) positive, negative, or normal
a reducing agent, can adversely affect reagent strip test results
Ascorbic acid
Ascorbic acid is a potential interfering agent that must be eliminated or detected through:
Chemstrip and vChem strip
uses an iodate overlay on the blood test pad to remove interference from ascorbic acid
Chemstrip
Refrigerated specimens must be allowed to return to ______ before reagent strip testing is performed (enzymatic reactions on the strips are dependent on temperature).
Room temperature
Care of Reagent strips:
- Store with desiccant in an opaque, tightly closed container
- Store below 30C; 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
is based on the change in pKa (dissociation constant) of a polyelectrolyte in an alkaline medium
Urine Specific Gravity
Hydrogen ions are released proportional to the number of ions in the solution as the polyelectrolyte ionizes
Urine specific gravity
Indicator in urine specific gravity chemical test:
Bromthymol blue (measures the change in pH)
As SG ↑es, bromthymol blue changes from ___________, through shades of _____________.
blue (1.000 [alkaline])
green, to yellow (1.030 [acid])
Higher urine concentration = higher hydrogen ions are released = ______ pH
Lower pH
Slightly increases the SG readings
Elevated protein concentration
indicator (the blue-green readings associated with an alkaline pH correspond to a low SG reading) →specimens with a pH of 6.5 or ↑= ↓SG readings
Bromthymol blue
when the pH is 6.5 or higher it is recommended to add _____ to the SG reading
0.005
Identify what type of test is used on these clinical significance:
Patient hydration and dehydration monitoring
Urine specific gravity
Identify what type of test is used on these clinical significance:
Diabetes insipidus
Urine specific gravity
Identify what type of test is used on these clinical significance:
Loss of renal tubular concentrating ability
Urine specific gravity
Identify what type of test is used on these clinical significance:
Verifying unsatisfactory specimens due to low concentration
Urine specific gravity
are the major regulators of the acid-base content in the body
Kidneys
pH of first morning urine
slightly acidic / pH 5.0 to 6.0
pH of following meals (alkaline tides)
more alkaline
pH or normal random samples
4.5 to 8.0
in normal or abnormal conditions, the pH of freshly excreted urine:
does not reach 9
pH of an improperly preserved specimen & indicates that a fresh specimen should be obtained
pH 9
double-indicator system of methyl red & bromthymol blue
Urinary pH
Urinary pH test has distinctive color changes from _____ through _____ to a final _______
orange at pH 5 through yellow & green to a final deep blue at pH 9
Methyl red color change from ______ in the pH range of _____
red to yellow
4 to 6
Bromthymol blue color changes from ______ in the pH range of _____
yellow to blue
6 to 9
Substances that interfere with urinary pH measurements performed by reagent strips:
No known substances
Identify what type of test is used on these clinical significance:
Management of urinary conditions that require the urine to be maintained at a specific pH
Urinary pH
Identify what type of test is used on these clinical significance:
Determining the existence of systemic acid-base disorders of metabolic or respiratory origin
Urinary pH
Identify what type of test is used on these clinical significance:
Acidic urine
Urinary pH
Identify what type of test is used on these clinical significance:
In persons with high-protein and high meat diets
Urinary pH
Identify what type of test is used on these clinical significance:
Ingestion of cranberry juice
urinary pH
Identify what type of test is used on these clinical significance:
Methanamine mandelate (Mandelamine) and fosfomycin tromethamine
urinary pH
in respiratory or metabolic alkalosis in vegetarians (digestion of fruits & veggies results to the formation of bicarbonates
alkaline urine
Identify what type of test is used on these clinical significance:
renal calculi formation
urinary pH
Maintaining urine at an ______ discourages formation of calculi
alkaline pH
precipitates primarily in acidic urine
calcium oxalate
the most indicative of renal disease
Protein
The first indicator of renal disease
Proteinuria
Protein content of normal urine (Strasinger):
<10 mg/dL or 100 mg per 24 hours excreted
Protein content or normal urine (Graff’s)
150 mg (1 to 14 mg/dL)
When the pH is held constant by a buffer (pH 3.0), indicator dyes release H+ ions because of the ______ present.
protein
Color change in protein ranges from ______
yellow to blue-green
The indicators change color in the presence of protein even though the pH of the medium remains _______
constant
Indicator dyes in protein:
tetrabromphenol blue (Multistix)
or
3′, 3′′, 5′, 5′′-tetrachlorophenol-3, 4, 5, 6-tetrabromosulfonphthalein (Chemstrip)
an _________ maintains the pH at a constant level
acid buffer
pH 3= both indicators are _______ = __________
yellow = ABSENCE OF PROTEIN
Protein Readings are reported in terms of:
negative, trace (1+, 2+, 3+, & 4+)
semiquantitative values of 30, 100, 300, or 2000 mg/dL
trace values: if <30 mg/dL
Sources of error in protein test:
highly buffered alkaline urine (pH >9)
False (+)
Major source of error with reagent strips
Highly alkaline urine
Sources of error in protein test:
pigmented specimens phenazopyridine quarternary ammonium compounds
False (+)
Sources of error in protein test:
antiseptics
False (+)
Sources of error in protein test:
Chlorhexidine
False (+)
Sources of error in protein test:
Loss of buffer form
False (+)
prolonged exposure of the reagent strip to the specimen ______
higher SG
Sources of error in protein test:
microalbuminuria
False (-)
Sources of error in protein test:
Proteins other than albumin
False (-)
Clinical proteinuria:
≥30 mg/dL (300 mg/L)
caused by conditions affecting the plasma prior to its reaching the kidney is not indicative of actual renal disease often transient e.g.,
Muscle injury
Multiple myoma
Acute phase reactants
Intravascular hemolysis
Prerenal
coagulates at temperatures between 40◦C and 60◦C and dissolves when the temperature reaches 100◦C.
Bence Jones protein
associated with true renal disease result of either glomerular or tubular damage
RENAL
Diseases under Postrenal
Injury/trauma
Menstrual contamination
Vaginal secretions
Prostatic
fluid/spermatozoa
Lower UTIs/ inflammation
