strip tests Flashcards
describe non-diabetic origin of glycosuria
- normal diet
- hormonal function (increase circulating blood glucose)
- renal tubule damge
describe renal glycosuria
glucose in the absence of hyperglycemia
- normal glucose in blood but still in urine
what causes renal glycosuria
renal tubule unable to reabsorb glucose (renal disorders)
describe the glucose strip test reaction steps
1) glucose -glucose oxidase + air -> gluconic acid and hydrogen peroxide
2) hydrogen peroxide -peroxidase + chromogen -> oxidized color compound
true or false:
glucose oxidase strip test is specific for only glucose
true
list false positive glucose reactions on a strip tests
contamination with: peroxide or oxidizing substances
list false negatives of glucose strip tests
- reducing substance (vitamin C)
- high specific gravity
- bacteria (from alone 2 hours)
why is first morning specimen not best for glucose UA
glucose can remain in bladder over night -> collect 2nd specimen
principle of clinitest
measures reducing substances and is not specific for glucose
- galactose, lactose, fructose and pentose
on what age of perosn was clinitest historically done
under 24 month old children to test for galactoemia
describe galactosemia
lack of galactoe-1-phosphate uridyl transferase enzyme causing lack of galactose -> glucose
why isn’t clinitest used anymore
- galactosemia is now part of new born screening tests using tandem mass spec
name the disorder:
clinitest pos
UA glucose dipstick neg
galactosemia
name the disorder
clinitest pos/neg (<200mg)
UA glucose dipstick pos
glycosuria
why are ketones monitored
- diabetes mellitus (deficiency of insulin)
- accumulation of ketones (acidosis, dehydration)
what intermediate ketone product is measured
acetoacetic acid
what does acetoacetic acid break down into
acetone and BHBA (other main intermediate products)
how are ketones measured on a strip test
sodium nitroprusside in alkaline medium
how does acetest differ from dipstick
tablet test with sodium nitroprusside and lactose for increased color differentiation
define hematuria and characteristic appearence
intact RBC in urine
red and cloudy
define hemoglobinuria and characteristic appearance
hemoglobin in urine due to RBC destruction
red and clear
define myoglobinuria and characteristic appearance
myoglobin in urine due to muscle destruction
red and clear
what is the clinically significant amount of red blood cells in urine
5 RBC/uL
what does the blood strip detect
- RBC
- hemoglobin
- myoglobin
how does the blood strip test detect RBCs, hgb and myoglobnin
all have pseudoperoxidase activity
define blood reaction on strip test
- peroxide and chromogen -(hgb peroxidase)-> oxidized chromogen
list causes of false pos blood strip
- strong ox reagents
- vegetable peroxidase
- bacterial peroxidase (e. coli)
list causes for false neg blood strip
- high levels of vitamin C
- reducing agents
list cuases of hematuria
- kidney stones
- glomerular disease
- tumor
-trauma - pyelonephritis (kidney infection)
- toxic substances
what causes RBCs to lyse in urinary tract
in dilute or alkaline urine
still hemoglobinuria
how is hemoglobin kept out of urine normally
hgb complexed with haptoglobin = too large to filter
how does hemosiderin form
reabsorption of filtered hemoglobin
where does hemosiderin normally accumulate
renal tubuluar epithelial cells (RTE) -> causes damage
how is myoglobin a probelm
breakdown product of skeletal muscle
toxic to renal tubule cells
can cause acute renal failure
describe the ammonium sulfate test
- differentiates myoglobin from hemoglobin
- ammonium sulfate binds hgb and forms sediment when spun
- myoglobin remains in supernatant when spun
- supernatent is then tested for blood
hemoglobinuria or myoglobinuria:
ammonium sulfate test was preformed and a new strip test was used on the supernatant
strip test pos for blood
myoglobinuria
what does the presence of bilirubin indicate
liver disease
- liver damage or bile duct obstruction
list steps in bilirubin breakdown
- RBC
- hgb
- protoporphyrin
- unconjugated bilirubin
- conjugated bilirubin (liver)
- urobilinogen (intestine)
- urobilin (feces)
what form of bilirubin is sent back to the liver and kidney
urobilinogen
what form of bilirubin in urine is indicative of bile duct obstruction
conjugated bilirubin
- liver is leaking conjugated material
descirbe the bilirubin strip test reaction
- diazo reaction
- bilirubin and diazonium salt in acid form azodye
what form of bilirubin in urine is indicative of liver disease or hemolytic disorders
urobilinogen
true or false:
absence of urobilinogen from urine and feces is clinically significant
true
- a small amount of urobilinogen should be in urine
what is ehrlichs reagent
part of urobilinogen detection
- p methylaminobenzaldehyde
what else will be pos in a ehrlichs reagent tube test
- urobilinogen tube test
- pos if porphobilinogen is present, indicans and antibiotics
- not urobilinogen specific
describe hoesch reagent
ehrlichs reagent in 6M HCl
when is hoesch screening test used
rapid screening test for urinary porphobilinogen
- red if porpho pos
- urobilinogen inhibited from acidic pH
why is nitrite tested
bacterial ability to breakdown nitrite to nitrate is significant
what test result is combined with nitrite to determine clinical significance
leukocyte esterase test
- bacteria and WBC response
what specimen is preferred for nitrite testing
first morning
list false negatives for nitrite test
- bacteria missing reducing enzyme
- GP and yeast present (no enzyme)
- ascorbic acid
list false pos for nitrite test
bacterial over growth from being left out (not fresh sample), color interference
describe what leukocyte esterase measures
presence of esterase in granulocytic white blood cells
- lysed cells
false pos for leukocyte esterase
pigmented urine, formalin
false negatives of leukocyte esterase test
ascorbic acid (binds dizonium)
crenated WBC
antibiotics
