Urinalysis Week 2

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)