3. Chemical Exam Flashcards
QC of reagent test strips happens when?
every 24 hours
new bottle opened
questionable results
concern about integrity
Why can’t the = control for reagent test strips be DI?
Needs to have a similar ionic concentration to urine.
confirmatory testing
use of different reagents or methodologies to detec the same subtances with the same or greater sensitivity or specificity
importance of pH on test srip
determining existence of systemic acid-base disorders
management of urinary conditions that require urine to be monitored at specific pH
2 major regulators of body pH
lungs
kidneys
how do the kidneys help regulate pH?
secrete H+ and ammonium ions
reabsorbing bicaronate ions
typical pH of first morning specimen
normal random sample pH range
5.0-6.0
4.5-8.0
(pH outside this range is physiologically impossible)
physiological causes of acidic urine (9)
- respiratory acidosis (emphysema)
- DM
- starvation
- dehydration
- diarrhea (base out the bottom)
- acid-producing bacteria
- high-protein diet
- cranberry juice
- medications
physiological causes of alkaline urine (6)
- respiratory alkalosis (hyperventilation)
- vomiting
- renal tubular acidosis
- vegetarian diet
- urease-producing bacteria
- old specimen
principle of pH reaction
- double indicator system
- methyl red + bromthymol blue
- yellow—acid; blue—alkaline
protein is most indicative of…
early renal disease
normal urine protein
< 10 mg/dL
100 mg/24 hours
proteinuria indicated at —- mg/dL
30
categories of proteinuria causes
- prerenal
- renal
- postrenal
proteins found in prerenal proteinuria
hemoglobins
myoglobins
acute phase proteins (infection, inflammation)
usually not detected by routine urinalysis, which detect primarily albumin
Bence Jones proteins are free ——-, and indicates….
monoclonal Ig light chains
multiple myeloma
method used to dx Bence Jones proteins
serum electrophoresis + immunoelectrophoresis
2 types of proteinuria of renal origin
- glomerular damage
- tubular dysfunction
most serious and most common type of proteinuria
glomerular damage
tubular dysfuntion leading to proteinuria is caused by less (filtration/reabsorption/secretion) of low MW proteins
reabsorption
examples of tubular proteinuria
Fanconi’s syndrome
heavy metal poisoning
severe viral infections
explain microalbuminuria
development of diabetic nephropathy leading to reduced glomerular filtration and eventual renal failure
type 1 and 2 DM
first predicts onset of renal DM complications
explain orthostatic proteinuria
increased pressure on the renal vein when in the vertical position causes proteinuria that goes away when you lay down
prinicple of protein reaction
- principle of protein error of indicators
- reagent pad is at pH 3, and proteins cause release of H+
- H+ turn indicator blue-green
confirmatory test for protein
sulfosalicylic acid precipitation test (SSA)
principle of SSA
- acid will precipitate proteins out of a solution, making the solution cloudy
- reacts equally with all forms of protein
most frequently performed chemical analysis on urine
glucose
renal threshold for glucose
160-180 mg/dL
2 types of causes of glycosuria
- hyperglycemia-associated
- renal-associated
examples of hyperglycemia-associated glycosuria
Diabetes mellitus
Pancreatitis
Pancreatic Cancer
Acromegaly
Cushing Syndrome
Hyperthyroidism
Pheochromocytoma
Central nervous system damage
Stress
Gestational diabetes
examples of renal-associated glycosuria
Fanconi Syndrome
Advanced renal disease
Osteomalacia
Pregnancy
failure to thrive
galactose in urine
lack galactose-1-phosphate uridyl transferase
principle of glucose reaction
- double sequential enzyme reaction
- includes glucose oxidase, peroxidase, chromogen, and buffer
- detects only glucose
vitamin C causes false —- glucose, blood, and bilirubin
negative
confirmatory test for glucose
copper reduction test
clinitest
benedict’s test
clinitest principle
- detects all reducing substances/sugars
- sugars reduce copper sulfate to cuprous oxide, colored green/red
pass through phenomenon
clinitest
high glucose levels
why don’t ketones normally show up in urine?
all the metabolized fat is completely broken down into carbon dioxide and water
3 ketones and percentages
- Beta-hydroxybutyrate (78%)
- Acetoacetic Acid (20%)
- Acetone (2%)
why does DM lead to ketoacidosis even when blood glucose is high?
without functioning insulin, the body cannot use the glucose that is available
clinical significance of ketonuria
Diabetic acidosis
Insulin dosage monitoring
Malabsorption/pancreatic disorders
Strenuous exercise
Vomiting
Eating disorders
Inborn errors of amino acid metabolism
principle of ketone reaction
- at an alkaline pH, acetoacetate reacts with sodium nitroprusside to produce a purple color
- only detects acetoacetic acid unless glycine is included, and then detects acetone also
confirmatory test for ketones
acetest
acetest principle
- tablet includes sodium nitroprusside and glycine
- turns purple with ketones
Reabsorption of filtered hemoglobin also results in the appearance of large yellow-brown granules of denatured —– called —— in the renal tubular epithelial cells and in the urine sediment.
ferritin
hemosiderin
brown recluse spider bites
hemoglobinuria
muscle destruction
rhabdomyolysis
statin medications
rhabdo
myoglobinuria
blood reaction principle
- pseudoperoxidase activity of hemoglobin to oxidize chromogen
- green-blue color
- reacts with RBCs, hemoglobin and myoglobin
—— cells can give false negative blood
crenated
2 types of bilirubin
- unconjugated/indirect: water insoluble, bound to albumin in blood stream - NOT in urine
- conjugated/direct: water soluble, can be found in urine
In the liver, bilirubin is conjugated with ——– by ———– to form ————-, commonly called conjugated bilirubin.
glucuronic acid
glucuronyl transferase
bilirubin diglucuronide
Bacteria in the intestines reduces the conjugated bilirubin to ———– and ————-.
urobilinogen
stercobilinogen
—-bilinogen can be reabsorbed or excreted in urine, and —-bilinogen cannot be reabsorbed and remain in intestine
urobilinogen
stercobilinogen
give stool its color
urobilin and stercobilin
clinical significance of bilirubinuria
Hepatitis
Cirrhosis
Other liver disorders
Biliary obstruction (gallstones, carcinoma)
bilirubin reaction principle
- diazo reaction
- conjugated bilirubin combines with diazonium salt to form azodyte
confirmatory test for bilirubin
ictotest
ictotest for bilirubin
—-% of urobilinogen is reabsorbed
2-5%
urobilinogen is quickly converted to —— on standing
urobilin
peak levels of urobilinogen
2-4 PM
normal urobilinogen
< 1 mg/dL
clinical significance of urobilinogen
Early detection of liver disease
Liver disorders, hepatitis, cirrhosis, carcinoma
Hemolytic disorders
Constipation
urobilinogen reaction principle
- MULTISTIX - Ehrlich’s aldehyde reaction - pink
- CHEMSTRIP - diazo reaction - red
limitation of urobilinogen test
cannot determine absence of urobilinogen
preservative that interferes with urobilinogen
formalin
Pre-Hepatic
unconjugated bilirubin
conjugated bilirubin
urine bilirubin
urine UBG
fecal UBG
unconjugated bilirubin ↑
conjugated bilirubin normal
urine bilirubin =
urine UBG ↑
fecal UBG ↑
Post-Hepatic
unconjugated bilirubin
conjugated bilirubin
urine bilirubin
urine UBG
fecal UBG
unconjugated bilirubin normal
conjugated bilirubin ↑
urine bilirubin +
urine UBG =
fecal UBG =, white color
why is the nitrite test important?
detecting initial bladder infection, because patients are often asymptomatic or have vague symptoms
nitrite reaction principle
- Greiss reaction
- nitrite + aromatic amine –> diazonium salt
- diazonium salt + tetrahydrobenzoquinolin –> pink azo dye
how to provide sufficient contact time for nitrite test
take first morning specimen
lack leukocyte esterase
lymphocytes
LE reaction principle
- acid ester + LE –> indoxyl aromatic compound
- aromatic compound + diazonium salt –> purple azo dye
trace amounts of LE are insignificant in ——
women
vaginal contamination
LE false positives with esterases found in…
histiocytes
trichomonas
helps us determine unsatisfactory specimens
SG
↑ SG = — pH change
↓SG = —- pH change
↓ pH
↑pH
reagent strip SG only detects…
ionic solutes
principle metabolite of ascorbic acid
oxalate
ascorbic acid is a strong —– because of its ene-diol group
reducing substance
(H+ donator)
reagent tests that use ——— or ——- are subject to vitamin C interference
H2O2
diazonium salt
4 test interfered with by vitamin C
- blood (H2O2)
- bilirubin (diazonium)
- nitrite (diazonium)
- glucose (H2O2)
ascorbic acid reaction principle
- action of ascorbic acid to reduce a dye
- blue to orange