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

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