Chemical Exam Confirmatory Testing Microscopic examination
What does the reagent strip consist of?
chemical-impregnated absorbent pads attached to a plastic strip
What do rapid means test for (reagent strip)?
pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocytes, and specific gravity
possible error/interferences
unmixed
extended immersion
run-over from other reagents
temp, humidity
interfering substances (AZO)
technical carelessness
color blind
Healthy pH ranges of urine
morning: acidic
following meals: alkaline tide
random samples: 4.5-8.0
What is the significance of urine pH?
diagnosis of resp./metabolic acid or alkalosis
renal calculi formation
treatment of UTIs
ID of crystals
defects in tubular secretion and reabsorption
pH pad reaction?
double-indicator system (methyl red and bromothymol blue)
Protein in the urine is most indicative of what?
renal disease
What protein is the reagent strip specific to?
albumin
Prerenal proteinuria
affects plasma before reaching kidneys
not discovered in routine urinalysis
Bence Jones proteins
Renal proteinuria
TRUE renal disease
glomerular membrane is damaged, selective filtration is impaired
What conditions, associated with renal proteinuria, are irreversible?
amyloid material
toxic exposure
lupus
strep glomerulonephritis
What reversible conditions are associated with renal proteinuria?
strenuous exercise
dehydration
hypertension
pre-eclampsia
Microalbuminuria
common for diabetes mellitus
diabetic nephropathy leads to dec glomerular filtration
prevented by control of blood glucose and hypertension
Orthostatic (postural) proteinuria
protein excreted when in vertical position
Tubular proteinuria
albumin can’t be absorbed anymore
toxic substance/heavy metal exposure
severe viral infections
Fanconi’s syndrome
Postrenal proteinuria
protein added to specimen after it passes through lower UT
bacterial/fungal infections, inflammatory conditions, menstrual contamination, trauma
Interferences that can cause false + on reagent strip for albumin:
highly buffered alkaline urine and pigmented specimens (AZO)
Interferences that cause false = on reagent strip for albumin:
proteins other than albumin or microalbuminuria
What system does the protein pad use?
protein error of indicators system
Glucose is filtered by …. and reabsorbed by ….
filtered: glomerulus
reabsorbed: PCT
A positive glucose result is indicative of what?
renal threshold reached
hyperglycemia (pancreatitis, thyroid issues, Cushing syndrome, hormones, and DIABETES)
Interferences for glucose reaction:
false +: contamination w/ peroxide or bleach (strong oxidizers)
false =: presence of reducing substances (ascorbic acid and salicylates)
glucose pad reaction:
glucose oxidase rxn (2 steps)
In what conditions would you find ketones in the urine?
fat is used as energy source
diabetes mellitus
bulimia
anorexia
keto diet
What does the ketone pad measure?
acetoacetic acid
What is the primary reagent in the ketone rxn?
sodium nitroprusside
interferences for the ketone reaction:
false +: pigmented urine, meds w/ sulfhydryl groups
false =: old/improperly preserved specimens
Presence of intact blood in the urine
hematuria (red and cloudy)
Presence of destructed blood in the urine
hemoglobinuria (red and clear)
Hematuria is related to?
disorders of renal or genitourinary origin
Hemoglobinuria is related to ?
disorders where the amount of free Hgb present exceeds the haptoglobin content
Myoglobinuria is related to?
disorders of muscle destruction
Interferences for the blood pad:
false +: oxidizing agents, povione-iodine, bacterial infections
false =: ascorbic acid, formalin, high protein/nitrites
What is the principle reaction of the blood pad?
pseudoperoxidase activity of Hgb
What is bilirubin?
degradation product of hemoglobin
Bilirubin in the urine can provide early indication of?
liver disease
Causes of bilirubinemia
hepatitis, cirrhosis, bile duct obstruction (gallstones), and pancreatic cancer
What are RBCs broken down into?
iron, protein, protoporhyrin (turned into bilirubin)
Interferences for bilirubin pad:
false +: pigmented urine, indican
false =: light exposure, ascorbic acid, high nitrites
Urobilinogen
produced from bilirubin by intestinal bacteria
liver disease or hemolytic disorders
What can cause a false negative urobilinogen result?
old specimen
light exposure (urobilinogen to urobilin)
inc nitrite
preservation in formalin
What can cause a false positive urobilinogen result?
porphobilinogen
highly pigmented urine
drugs
testing after eating
What is the reaction called on the bilirubin pad?
diazo reaction
What is the main reagent on the urobilinogen pad?
Ehrlich reagent
bile duct obstruction bili/urobili results
+ bili normal urobili
liver damage bili/urobili results
pos or neg bili pos urobili
Hemolytic disease bili/urobili results
neg bili pos urobili
What does the nitrite test show?
presence of bacteria in the urine (UTI and the itises)
What is the name of the nitrite rxn on the pad?
Greiss reaction
Nitrite pad interferences
false +: pigmented or old urine
false =: high SG, ascorbic acid, urobili
Leukocyturia
WBCs in urine
What is the Leukocyte esterase test looking for?
presence of esterase in granulocytic WBCs and monos (doesn’t measure conc.)
what type of reaction is used on the LEU pad?
hydrolysis
interferences on the LEU pad:
false +: oxidizing agent, formalin, eos, trichomonas
false =: high protein, glucose, and SG, ascorbic acid, antibiotics
rection for SG pad
change of pka in an alkaline medium
interferences of SG pad:
false +: high protein
false =: high protein or high alkaline
What is the confirmatory test for reducing agents?
Copper reduction test (Clinitest)
Confirmatory test for bilirubin
Ictotest tablet
Confirmatory test for Ketones
acetest
Confirmatory test for protein
sulfosalicylic acid test
What is the principle of the Clinitest?
substances reduce copper sulfate to cuprous oxide in the presence of alkali and heat (blue > orange)
What is the original version of the Clinitest?
Benedict’s Principle (urine > heat > color)
It is important to be cautious with the Clinitest because?
the tube generates a lot of heat (could burn your hand)
Pass-through phenomenon
extremely elevated glucose levels (or other reducing subs) can cause the rxn to return to blue from orange
The Clinitest is positive and the glucose dipstick is negative, what might cause this?
inherited enzyme deficiencies
lactosuria (nursing moms)
pentosuria (eating certain fruit)
frutosuria (fruit or fructose)
galactosuria
What makes galactosuria most clinically significant?
found in newborns, inborn error of metabolism, results in failure to thrive
What population is the Clinitest method used on?
children under 2 for galactosemia
hygroscopic
tends to absorb or attract moisture from air
What is the color you are looking for on the Acetest?
purple (positive)
If bilirubin is present, what color appears on the mat?
blue-purple
What methods of testing can be used to screen for diabetic nephropathy?
immunochemical (Micral-test) methods w/ anti-albumin Ab
ImmunoDip
Which historic test is used on high alkaline urines ? and why?
sulfosalicylic acid precipitation test, used because high pH leads to false positives
This common cause of proteinuria is excreted in multiple myeloma
Bence Jones Protein
Birefringent
the ability to refract light in 2 directions
Kohler illumination
adjustments made to the microscope condenser when objectives are changed
Resolution
the ability to separate fine structure for visualization of detail
Ocular lens
lens closer to the eye (power of 10X)
objective lens
lens closer to object
What is the formula for total magnification?
ocular magnification X objective power
What does the field diaphragm control?
the diameter of the light beam reaching the slide
Condenser
focuses light on the specimen
Rheostat
controls the intensity of the light produced by the condenser (turn up if there is too much light focused)
What is the most common method of microscopy in the clinical lab?
Bright-field
Phase-contrast microscopy
good for looking at casts and mucous in urine (requires special lens, condenser and phase rings)
polarizing microscopy
used for crystals, lipids, etc.
What step in urinalysis is microscopy?
3rd (physical > chemical > microscopy)
What are the normal ranges for cells in the urine?
RBCs: 0-3 cells/hpf
WBCs: 0-3 cells/hpf
hyaline casts: 0-2 /lpf
Clinical significance of RBCs in urine
damage to glomerular membrane or vascular injury
# of cells indicates how bad damage is
Microscopic hematuria
early diagnosis of glomerular disorders, malignancy, confirm renal calculi
What do dysmorphic RBCs in urine indicate?
glomerular bleeding
Ghost cells indicate:
non-glomerular bleeding (dilute urine lysed RBCs)
A high number of WBCs could indicate what?
pyuria or leukocyturia (infection or inflammation)
If neutrophils are the predominant WBC found, what could this mean?
hypotonic urine (glitter cells due to Brownian movement of granules)
What would you suspect if eosinophils were the predominant WBC seen?
drug induced interstitial nephritis
low amount in UTI or renal transplant rejection
When would mononuclear cells be increased?
early stages of renal transplant rejection
If epithelial cells are found in the urine, where do they come from?
linings of genitourinary tract
represent normal sloughing of old cells
Clue cells
squamous cell covered in G. vaginalis (observed more in wet prep)
Renal Tubular Epithelia (RTE)
PCT cells never seen in large sheets
DCT cells are smaller than PCT
collecting duct cells seen in large sheets (present in necrosis)
oval fat bodies
seen in lipiduria (glomerular damage, tubular necrosis, diabetes, release of bone marrow trauma)
What is the most common species of yeast found in urines? in which populations?
Candida albicans (diabetic, immunocompromised, women w/ yeast infections)