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138 terms

chapter 7

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what is always reported out with SG and pH test results
numbers
reagent strip advantage
provides a means of rapidly screening large numbers of urine specimens in a timely fashion for pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, and leukocyte esterase
are the chemical principles used on reagent strips basically the same
yes
depending on the brand used, what can also be screened by reagent strips
specific gravity and ascorbic acid
Multistix, chemstrips, rapignost
three common brands of ragent strips
care and storage of reagent strips
protect from light, moisture and heat
when do you do a QC test on reagent strips
-when you open a new bottle
-when you receive a new lot #
-daily
what three things are tablet tests susceptible to
light, heat and moisture
what should you do before you use a tablet for testing
inspect it for deterioration and discard if it's discolored, contaminated, was incorrectly stored, spoiled, or past the expiration date
what kind of specimen should you use for chemical testing (reagent strips)
a fresh, well-mixed, uncentrifuged urine specimen at room temp and under 2 hrs old (otherwise put it in fridge) **Note: always allow cold specimens to warm to room temp before testing
testing technique for reagent strips
dip the reagent strip briefly into the specimen, making sure all test pads are wet
what can cause contamination of one reagent strip test pad with the ragents from another pad
inadequate removal of excess urine from the strip
what causes chemicals to leach from a reagent test strip pad into a specimen
prolonged dripping of the strip in the specimen
after what amount of time are color changes on a test strip pad insignificant
2 minutes
what specimen characteristic can cause a false color readout on a test strip pad
highly pigmented urines
specific gravity
physical property of urine, an expression of concentration
isosthenuria
when the specific gravity of urine excreted is the same as the specific gravity of the original ultrafiltrate (plasma)
what test result implied significant renal tubular dysfunction
isosthenuria
hyposthenuric urine
urine specimens with a SG of less than 1.010
Hypersthenuric urine
urine specimen with a SG of over 1.010
normal urine SG
1.002-1.035
what should you do in the lab if your specimen has a SG outside normal range
check the specimens with a a second method and make sure your QC is ok
what can cause your specimen SG to exceed 1.025
excessive sweating, dehydration, or fluid restriction
SG method
ionic colutes present in the uring cause protons to be released from a polyelectrolyte. As the protons are released, the pH decreases and produces a color change of the Bromthymol blue indicator from blue-green to yellow-green.
what three things control your body pH
renal system, pulmonary system, and blood buffers
4.5-8.0
normal urine p
what could be used to check urine pH
pH paper
pH meter
reagent strip
why is urine usually slightly acidic
because endogenous acid production predominates
alkaline tide
during and after a meal, the stomach secretes acid to aid digestion which makes the urine less acidic
under 4.5 or over 8.0
pH values of urine that are physiologically impossible- require investigation
pH methodologies
double indicator system using Bromthymol blue and Methyl red
pH color indicator meanings on a strip
the more blue- the more alkaline
green= pH of 7
what can cause pH result errors
-improper specimen storage with bacterial proliferation (false increase of pH)
-contamination of specimen container before collection
-improper reagent strip technique
pH meter characteristics
a silver-silver chloride indicator electrode with a pH sensitive glass membrane connected by a salt bridge to a reference electrode
with a pH indicator electrode, when it is place in urine, a difference in the H+ activity develops across the glass membrane, which causes:
a change in the potential difference between the indicator and reference electrodes
pH test papers will...
produce sharp color changes for comparison to a supplied color chart of pH values
could blood be present in urine if the urine is clear
yes
where does blood in urine come from
can be from anywhere in the urinary tract from the glomeruli to the urethra, or it can be a contaminant from the collection procedure
to RBC's easily lyse in alkaline or acidic urine
alkaline
is true hemoglobinuria common or uncommon
uncommon
hematuria
describes an abnormal amount of RBCs in urine
hemoglobinuria
indicates presence of Hgb in urine
name of another substance that contains heme groups
myoglobin
Myoglobin easily passes the glomerular filtration barrier, what can cause an increase in myoglobin in urine
muscle damage during trauma or disease
what three things can cause a positive chemical test for blood
RBCs, hemoglobin or myoglobin
what three things differentiate hematuria from hemoglobinuria
urine clarity, color and pH
hematuria characteristics
urine is cloudy, (clear in hemoglobinuria)
what can cause hematuria or hemoglobinuria
kidney disease, urinary tract disease, trauma, drug therapy, or strenuous exercise
detection of RBCs or Hgb is an early indicator of disease that's not always evident visually and always requires
an investigation
does the amount of blood in urine correlate to the severity of disease
no
what kind of condition has the potential for producing hemoglobinuria
any condition resulting in intravascular hemolysis
Hgb can be reabsorbed in porximal renal tubules and catabolized to WHAT, then denatured to WHAT
ferritin, and hemosiderin (the storage form of iron)
in a hemolytie transfusion reaction:
no bilirubin will be found but urobilinogen will be high
what is a sign of reduced tubular function
casts
what is the name for RBCs in a protein cast
Tam Hastfall protein - or - uromodulin
rous test
prussian blue staining test
prussian blue staining test
used on concentrated urine sediment to help see the hemosiderin
what can cause traumatic myoblobinuria with acute renal failure
alcohol overdose or Hx of cocaine or heroin addiction
hemoglobinuria characteristics
red or brown urine with hemolyzed blood plasma
myoblobinuria characteristics
pink, red, or brown urine with clear blood plasma
myoglobin method
ammonium sulfate precipitation
blood testing methodology
pseudoperoxidase activity of the heme moiety
blood test:
intact RBCs are lysed on the pad, releasing Hgb, and ausing a mottled green or dotted pattern on the pad
how is blood urine reported
neg, trace, small, moderate, or large (or numerical 1+ 2+ 3+ 4+)
is Hgb detectable in urine before or after centrifugation
both- it will not settle out during centrifugation because it's dissolved in the urine
what can interfere with blood reagent strips
vit C
what do chemstrips have that eliminates the interference with vitamin C in a blood test
an iodate scavenger pad
for leukocyte esterase testing, what does the strip pad detect
granulocytes only (so lymphocytes won't be detected)
what do significant numbers of WBC's in urine indicate
inflammation anywhere in the kidneys or lower urinary tract
now many WBCs are normal to have in urine
0-2
why are there increased numbers of WBCs found more often in women than in men
-partly because of more UTIs in women
-partly because of vaginal secretion contamination in urine
what can we detect even if WBCs have lysed
leukocyte esterase
bacteriuria
bacteria in urine
leukocyturia
WBCs in urine
Leukocyte esterase methodology
based on the action of the leukocyte esterase to cleave an ester to an aromatic compound
although a dipstick may initially detect 10-25 WBCs...
negative result does not rule out presence of increased urine WBCs
what can cause leukocyturia false positive
drugs or foods that color theurine red in an acid medium, because they mask the reagent pad with their color and ppear positive
what is an important tool to use for UTI screening
nitrite screen
what is the most common organism in UTI's
escherichia coli (E-coli)
what are common organisms in UTI's
proteus, enterobacter and klebsiella
what can cause UTIs to start
an obstruction, bladder dysfunction, or urine stasis
list four factors required for positive nitrite test
1. GNB (gram negative bacilli)
2.Gram negative bacilli that's a nitrate reducer
3. urine in the bladder equal to or greater than 4 hours
4. dietary nitrate must be available for gram negative bacilli to use or convert
Nitrite methodology
diazotization reaction of nitrite with an aromatic amine to form a diazonium salt, followed by an azocoupling reaction with another aromatic compound to form an azo dye and a color change (white to pink)
how much filtered protein is reabsorbed
95-99%
why do we only see a small amount of albumin in urine
it has a hight plasma concentration, moderate molecular weight, and limited ability to go through glomerular filtration
Uromodulin, or tamm horsfall protein (methodology)
a mucoprotein synthesized by the distal tubular cells and involved in cast formation
urokinase
a fibrinolytic enzyme secreted by tubular cells
secretory immunoglobulin A
synthesized by renal tubular epithelial cells
proteinuria
presence of increased amount of protein in urine (often first indicator of renal disease)
what can cause increase urine albumin
proteinuria
three characteristics of protein reabsorption by the renal tubules
nonselective, competitive, and threshold-limited
what do you see in urine when you have prerenal proteinuria or overflow proteinuria
abnormal paraproteins in multiple myeloma and macroglobulinemia
renal proteinuria
glomerular or tubular or a combination
renal glomerular proteiuria categories
selective: increase in albumin
nonselective: increase in all proteins
what can cause proteinuria to develop
nephrotic syndrome
what diseases is albumin excretion most important in
diabetes, hypertension, and peripheral vascular disease
fanconi's syndrome
characterized by proximal tubular dysfunction, includes aminoaciduria, proteinuria, glycosuria, and phosphaturia. can be hereditary
postrenal proteinuria
proteins produced by the urinary tract
postural proteinuria
a functional proteinuria
functional proteinurias
transitory, induce a mild glomerular or mixed pattern proteinuria in absence of renal disease
protein methodologies
qualitative or semiquantitative
what causes proteins to coagulate
heat
sulfosalicylic acid precipitation test
ssa
protein methodology for reagent strips
protein error of indicators- more sensitive to albumin than any other protein
why is monitoring low-level albumin excretion important for patients with diabetes, hypertension, or peripheral vascular disease
these patients will develop low -level albuminuria before they present clinically with nephropathy
micral test
reagent strips specific for screening low-levels of albumin
glucosuria and glycosuria
presence of glucose in the urine
what can cause glucose to spill into the urine
when the renal threshold has been reached (160-180 mg/dL)
hyperglycemia
a prerenal glucose condition
defective tubular absorption
a renal condition
galactose
most significant besides glucose
galactosemia
a disease with severe and irreversible consequences
lactose
sugar in milk
signs of lactose intolerance in infants
failure to thrive, vomiting, and diarrhea
what are the only pathologic sugars in urine
glucose and galactose
what must you test for in you want to detect anything other than glucose in urine
reducing substances
glucose methodology
double sequential enzyme reaction. this only detects glucose!
benedicts test
clinitest (copper reducing test) for reducing substances
3 ketone bodies
acetoacetate
beta-hydroxybutyrate
acetone
ketonemia
large amounts of ketones released into the blood
ketonuria
ketones excreted in the urine. this only happens with blood concentration exceeds 70 mg/dL
ketonuria symptom
fruity breath
ketonuria is an early indicator of what
insulin deficiency
what happens if you don't treat ketonuria
chemical imbalance
acidosis
diabetic coma
ketone methodology
nitroprusside reaction
is beta hydroxybutyrate detected by a reagent strip
no
acetest
nitroprusside tablet test for ketones
what type of bilirubin is soluble
conjugated- in the liver
heme breakdown
results in biliverdin production
prehepatic bilirubin buildup
urine bilirubin negative, urine urobilinogen increased
hepatic bilirubin buildup
urine bilirubin increased, urine urobilinogen increased or normal
posthepatic bilirubin buildup
bile duct or biliary tree is obstructed- so feces will appear acholic because normal bile pigments are missing
bilirubin methodologies
based on the coupling reaction of a diazonium salt on the pad, with bilirubin in an acid medium to form an azo dye, giving a color change from light tan to beige or pink
ictotest method
diazo tablet test for bilirubin- if you have a positive bili on strip, always do an ictotest fo confirm
urobilinogen methodology
classic ehrlich's reaction- based on reaction of urobilinogen with p-dimethylaminobenzaldehyde
porphobilinogen
needed to make heme, which is needed to make hemoglobin
porphobilinogen methodologies
physical exam, colorless and nonfluorescent, and it's oxidized form IS colored dark red
test used for porpherines
hoesch test and watson schwartz test