Urinalysis - Chemical Urinalysis by Reagent Strip Flashcards
What is the normal pH of a first morning specimen?
5-6
What is the normal pH of a random urine specimen?
4.5-8
What is the principle of a pH test?
double indicator system
What is the significance of urine pH?
-acid-base balance
-management of urinary tract infections & renal calculi
pH with a protein/meat diet
acid
pH with a vegetarian diet
akaline
What is the pH of a improperly preserved urine specimen?
9 or above
What is the normal value for urine protein?
negative to trace
What is the principle of a urine protein test?
protein error of indicator
What is the significance of urine protein?
possible renal disease
In a solution that does not contain protein, tetrabromphenol blue, buffered at a pH of 3, is what color?
yellow
What protein is the urine protein test most sensitive to?
albumin
What would protein results look like in orthostatic proteinuria?
-protein would be negative in the first morning sample
-protein would be positive after standing
What is the normal range for glucose in a urine sample?
negative
What is the principle of a urine glucose test?
glucose oxidase/peroxidase
What is the significance of a positive glucose result?
possible diabetes mellitus
What is the normal renal threshold for glucose?
160-180 mg/dL
Is the glucose urine test specific for glucose?
yes
What is the normal range for urine ketones?
negative
What is the principle for the urine ketone test?
sodium nitroprusside reaction
What is the significance of ketones in urine?
increased fat metabolism due to uncontrolled diabetes, vomiting, starvation, low carb diet, or strenuous exercise
What is the ketone urine test most sensitive to?
acetoacetic acid
(less sensitive to acetone)
Does the ketone urine test react with beta-hydroxybutyric acid?
no
What is the normal range for blood in urine?
negative
What is the principle of the urine blood test?
pseudoperoxidase activity of hemoglobin
What is the significance of blood in urine?
-hematuria
-hemoglobinuria
-myoglobinuria
What does the reagent strip for blood look like if it is positive due to hemoglobin or myoglobin?
uniform in color
What does the reagent strip for blood look like if it is positive due to red blood cells?
speckled
What is the normal range for bilirubin in urine?
negative
What is the principle of the urine bilirubin test?
diazo reaction
What is the significance of a positive urine bilirubin?
-liver disease
-biliary obstruction
What type of bilirubin is excreted in urine?
ONLY conjugated bilirubin
What is the normal range for urine urobilinogen?
1 Ehrlich unit or 1 mg/dL
What is the principle of the urine urobilinogen test?
Ehrlich aldehyde reaction OR diazo reaction
What is the significance of an increased urine urobilinogen result?
-liver disease
-hemolytic disorders
Do urine reagent strips detect the absence of urobilinogen?
no, they only detect increases
What is the normal range for urine nitrites?
negative
What is the principle of the urine nitrite test?
Greiss reaction
What is the significance of a positive urine nitrite?
UTI
Why would a nitrite test be positive in cases of UTIs?
some bacteria reduce nitrates to nitrites
Why is a first morning specimen ideal when testing for nitrites?
increased sensitivity when urine has been in the bladder for at least 4 hours
What is the normal range for urine leukocyte esterase (LE)?
negative
What is the principle of the leukocyte esterase test?
leukocyte esterase reaction
What is the significance of a positive leukocyte esterase?
UTI
What does the leukocyte esterase test detect?
intact and lysed granulocytes and monocytes, NOT lymphocytes
What urine reagent strip tests can be used to screen urines for culture?
nitrite and leukocyte esterase tests
What test on a urine reagent strip has the longest reaction time?
leukocyte esterase (2 minutes)
What is the normal range for urine specific gravity?
Random specimen: 1.003-1.030
What is the principle for a urine specific gravity test?
pKa change of polyelectrolyte
What is the significance of specific gravity?
-indication of the kidney’s concentrating ability & state of hydration
Why is specific gravity increased in diabetes mellitus?
glucose
Why is specific gravity decreased in diabetes insipidus?
decreased ADH
What is reagent strip specific gravity NOT affected by?
-urea
-glucose
-radiographic contrast media
-plasma expanders
Possible effect of failure to test urine within 2 hours of collection or to preserve correctly
changes in chemical composition
Possible effect of failure to bring refrigerated specimens to room temperature before testing
false-negative enzymatic reactions
Possible effect of failure to mix specimen well
false-negative leukocyte, blood
-WBCs and RBCs settle out
Possible effect of failure to perform quality control
erroneous results
When should quality control for reagent strips be done?
every 24 hours and when opening a new container
Possible effect of failure to dip all test pads in urine
false-negative reactions
Possible effect of prolonged dipping of the reagent strip into urine
false-negative reactions
-reagents may leach from pads
Possible effect of failure to remove excess urine from the reagent strip
runover of chemicals to adjacent pads, distortion of colors
Possible effect of failure to read at recommended time
erroneous results
Possible effect of highly pigmented urine
atypical colors, false-positive reactions
-pigment masks true reactions (should test by alternate methods)
Possible effect of failure to store test strips properly
erroneous results
How should urine reagent strips be stored?
in capped original container at RT
What would cause an increased pH on a reagent strip?
improperly preserved specimen
What would cause a decreased pH on a reagent strip?
acid runover from protein square
What would cause a false positive protein result on a reagent strip?
-highly buffered alkaline urine
-prolonged dipping
-contaminated container
-increased specific gravity
What would cause a false negative protein on a reagent strip?
proteins other than albumin
What would cause a false positive glucose on a reagent strip?
contamination with peroxide or bleach
What would cause a false negative glucose on a reagent strip?
-improperly preserved specimen
-increased ascorbic acid
-increased specific gravity
-decreased temperature
What would cause a false positive blood result on a reagent strip?
-menstruation
-oxidizing agents
-bacterial peroxidase
What would cause a false negative blood result on a reagent strip?
-increased ascorbic acid
-increased nitrite
-increased specific gravity (crenated RBCs)
-unmixed specimen
