Test 3: Review Flashcards by Sarah King

What are the handling requirement’s for reagent strips?

-Store with desiccant in an opaque, tightly sealed container
-Remove strips immediately –prior to use
-Store below 30C
-Do not use past the expiration date
-Visually inspect for discoloration/deterioration

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Why is it important to mix specimens before testing?

Formed elements such as red and white blood cells sink to the bottom of the specimen and will be undetected in an unmixed specimen

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What happens when a urine specimen remains at room temp for an extended period of time?

Bacteria can begin to grow rapidly causing a falsely alkaline urine and give the urine a cloudy-hazy appearance.

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How do reagent test strips work for testing blood?

The pseudoperoxidase action of erythrocytes and hemoglobin catalyzes the oxidation of various chromogens to produce the color change.

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What can cause false positives on the blood reagent test strip?

oxidizing contaminants (bleach), microbial peroxidase. Very sensitive.

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What can cause false negatives on the blood reagent test strip?

formalin, excess nitrites, elevated specific gravity and Captopril may reduce reactivity.

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How do reagent test strips work for testing bilirubin?

Bilirubin in the urine couples with a diazonium salt in an acid medium.

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What can cause false negatives on bilirubin test strips?

samples exposed to light will show decreased amounts of bilirubin; excess levels of ascorbic acid.

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What can cause false positives on bilirubin test strips?

highly colored metabolites of drugs may interfere with reading the reaction and appear as false positives.

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How do the reagent test strips work for testing glucose?

The color is produced through a double enzymatic reaction of glucose oxidase and peroxidase. The latter enzyme reacts with a chromogen to produce the final color.

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What can cause false negatives on glucose reagent test strips?

elevations of ketones; very elevated specific gravities; excess levels of ascorbic acid.

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What can cause false positives on glucose reagent test strips?

presence of oxidizing agents (bleach).

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How do the reagent test strips work for testing ketones?

Ketones react with nitroprusside or sodium nitroferricyanide and glycine to produce a color change.

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What can cause false positives on ketone reagents strip testing?

presence of phenylketone or phthalein compounds; highly pigmented urines; some drug metabolites.

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What are the limitations with ketone reagent strip testing?

Only detects acetoacetate and acetone, not Beta hydroxybutyrate that is common in diabetes and nutritional disorders.

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How do reagent test strips work for testing nitrites?

Nitrates in the urine are converted to nitrites by the action of gram negative bacteria. These nitrites then react to form a diazonium salt which in turn reacts with a chromogen to produce the final color.

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What can cause false negatives with nitrite reagent test strips?

excess ascorbic acid. Animals false negatives; not reliable.

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What can cause false positives with nitrite reagent test strips?

presence of red dyes or other chromogens.

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How do reagent test strips work for testing pH?

A double indicator system detects the amount of hydrogen ions in the urine to produce a color change.

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What animals usually have more acidic pH?
What animals usually have a more alkaline pH?

carnivores

herbivores

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What testing error can cause issues with pH reagent test strips?

If excess urine is left on the reagent strip, a phenomenon known as runover may occur. The urine from one reagent area carries reagent onto the pH test area and changes the result erroneously.

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How do reagent test strips work for protein?

: This reaction is based on the phenomenon known as the “protein error of indicators” where an indicator that is highly buffered at a pH of 2 will change color in the presence of proteins (anions) as the indicator releases hydrogen ions to the protein.

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What can cause false positives on protein reagent test strips?

Strongly basic urine; presence of phenazopyridine, polyvinylpyrrolidone, chlorhexidine, and bleach.

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What will give the best sample for urobilinogen testing?

Excretion of urobilinogen is enhanced in alkaline urine, a sample that is voided two hours after a meal is best.

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How do reagent test strips work for urobilinogen?

Urobilinogen reacts with a chromogen to form an azo dye which appears as various shades of pink or purple. This reaction occurs best at room temperature.

What can cause false negatives with urobilinogen reagent test strips?

Excess nitrites; presence of formalin.

What can cause false positives with urobilinogen reagent test strips?

Presence of phenazopyridine; very warm urine.

How do reagent test strips work for leukocytes?

Leukocyte esterase, present in granulocytes, catalyzes the reaction of the chromogens to produce a color change.

What can cause false negatives with leukocyte reagent test strips?

Gentamicin, elevated glucose and protein concentrations, tetracycline.

What can cause false positives with leukocyte reagent test strips?

Drugs producing red urine, vaginal contamination. Notes: Generally not reliable in animals.

How do reagent test strips work for specific gravity?

This reaction is based on change of an indicator color in the presence of high concentrations of various ions.

Test strips for specific gravity are not reliable in animals. Scale is not high enough for many species. What should be used to get a reliable reading?

refractometer

Confirmatory test that will detect other sugars such as lactose, fructose, galactose, and pentoses. These other sugars may signify metabolic disorders when found in the urine of small children

Clinitest - Copper reduction test

Ketone test that can be used as a backup or to evaluate questionable results, but affected by same interferences seen on dipstick

ACEtest for Ketones

True or false: The ACEtest is a ketone confirmatory test?

False

What does a positive result look like for the ACEtest?

varying levels of purple = positive no color change = neg.

What does the ACEtest for ketones tablet contain?

sodium nitroprusside, glycine, disodium phosphate, lactose (gives better color)

What is the confirmatory test for bilirubin?

ICTOtest – Diazo Tablets

What is the difference between bilirubin strip tests and the ICTO test?

Same principle as strip but picks up LOWER levels

What does a positive ICTO test look like?

Positive = blue-to-purple color

For example, what does it mean if ketones or blood reactions are positive?

Ketones are formed during the catabolism of _________.

fatty acids

A positive ketone test may signify diabetic ___________.

ketoacidosis

Any amount of BLOOD greater than ____ cells per microliter of urine is considered clinically significant.

What is it called when there are intact RBCs in the urine? Can make a cloudy red appearance.

Hematuria

What are possible causes of hematuria?

-Glomerular disease -Pyelonephritis or cystitis -Renal calculi -Tumor -Trauma, hypertension, exercise, smoking, meds and other toxins

product of RBC destructions – clear red urine

Hemoglobinuria

What are possible causes of hemoglobinuria?

-Intravascular hemolysis from transfusion reactions, hemolytic anemia, paroxysmal nocturnal hemoglobinuria -Infections – malaria -Chemical toxicity – copper, nitrates, nitrites -Exertional hemolysis

Anything over ____ WBCs/mL indicates pathological problems such as inflammation or infection

Leukocyte esterase detects the presences of...

lysed leukocytes

What must be done if Leukocyte esterase (LE) is positive on dipstick and why?

have to do microscopic test because it is not considered a quantitative test

What can cause false positive with leukocyte esterase dipstick testing?

-Presence of vaginal contamination -Highly pigmented urine (nitrofurantoin, beets)

What can cause false negatives with leukocyte esterase dipstick testing?

-High concentrations of protein, glucose, high SG -Presence of antibiotics, gentamicin, cephalosporins, tetracyclines or other strong oxidizers

Dipstick positive + proportionate number of RBCs on microscopic UA =

hematuria

Dipstick positive + disproportionately low or absent RBCs on microscopic UA =

hemoglobinuria/myoglobinuria

Dipstick negative (rarely 1+) + no RBCs on microscopic UA =

pseudohematuria

when the urine sample is centrifuged, the ___________ is red in hematuria and the _____________ is red in hemoglobinuria, myoglobinuria, or drug/dye-induced discoloration.

sediment supernatant

What tests are positive if you see casts?

protein

___________ bilirubin is increased - bile duct obstruction, liver disease, or damage.

Conjugated -Obstruction: bilirubin backs up into circulation and is excreted in urine.

With hemolytic disease what types of bilirubin are increased?

unconjugated bilirubin and urobilinogen

What type of bilirubin is increased with Hepatitis and cirrhosis?

-Conjugated bilirubin leaks back into circulation from damaged liver -Some bilirubin passes to intestine

Large quantities with WBCs and/or white cell or mixed casts indicate the presence of _____________.

pyelonephritis

What casts are associated with Acute pyelonephritis? With pyelonephritis?

Hyaline casts White blood cell casts

What microscopic finding is associated with cystitis?

White blood cells

What changes occur in a specimen over time?

Increased: color, turbidity, pH, nitrite, bacteria, and odor. Decreased: glucose, ketones, bilirubin, urobilinogen, RBCs, WBCs, casts (due to breakdown or oxidation)

What microscopic changes in unpreserved urine occur over time?

-Formed elements tend to disintegrate, especially in alkaline urine -Formed elements are WBCs, RBCs, and casts

Macroscopic changes of urine over time?

-Amorphous crystals may form causing a pink color, uroerythrin. (no clinical significance) -Amorphous urates – brownish-red “brick-dust sediment” -Amorphous phosphates – Gray-white sediment

What crystals can be seen in normal acid urine?

-Amorphous urate -Uric acid -Calcium oxalate crystals

What crystals can be seen in normal alkaline urine?

-Amorphous phosphates - Triple phosphate - Ammonium biurate - Calcium phosphate - Calcium carbonate crystals

Hypertonic urine can cause.... Hypotonic urine can cause...

crenated RBCs ghost cells

What is the clinical significance of many squamous cells?

may mean contamination from not cleaning the genital area properly.

Identify

Squamous epithelial cells

Are transitional epithelial cells ever considered abnormal or an indication of disease?

in high numbers can indicate disease of the bladder or renal pelvis, or use of a catheter.

How are transitional cells differentiated from RTE?

by a centrally located nucleus in transitional epithelial cells

Are transitional epithelial cells clinically significant?

Mostly no clinical significance?

-A few are normal -These cells indicate pathology: enumerate and report

Renal epithelial cells

Which will have a clear supernatant after centrifugation of urine? a. hematuria b. hemoglobinuria c. myoglobinuria

a. b. and c. will not!

How to differentiate hemoglobinuria from myoglobinuria?

evaluate the plasma color; hemoglobinuria will have a pink to red plasma color, whereas myoglobinuria will not.

Formed from plasma proteins and/or Tamm-Horsfall mucoprotein

Hyaline Casts

Which cast is the basis upon which all casts are formed?

Hyaline Casts

Increased number of hyaline casts is associated with:

-Acute glomerulonephritis -Acute pyelonephritis -CHF -Chronic renal failure

-Dissolve easily in alkaline urine -Low refractive index

Hyaline Casts

Larger diameter and believed to be formed in renal tubules which have undergone dilation

Broad Casts

What are broad casts usually composed of?

consist of renal tubular epithelial cells (also WBCs and RBCs) An be degenerated to become granular, then waxy

Referred to as “renal failure casts”

broad casts

Indicate degenerative renal diseases caused by hypertrophy of tubules and ducts, which results in excessive urea absorption.

broad casts

What diseases are broad casts associated with?

Acute tubular necrosis, severe chronic renal disease, and urinary tract obstruction

Prognosis is grave when this casts type is found in numbers

broad casts

Identify the cast

Hyaline cast

Broad cast

-Represent final phase of cellular degeneration -Identified easily due to sharp refractive outlines -“Broken off” ends

Waxy casts

What are waxy casts associated with?

Indicates extreme urine stasis, seen with: -Chronic renal disease/failure -Kidney disease from diabetes mellitus -Numerous waxy casts indicate a fairly long renal transit time

What are White blood cell casts associated with?

Pyelonephritis

What are white blood cell casts usually accompanied by?

large number of WBCs in sediment, proteinuria, and bacteriuria

White blood cell casts plays a secondary role in...

acute glomerulonephritis

What casts ALMOST ALWAYS indicate renal disease?

Red blood cell casts

Red blood cell casts Usually occur in diseases where the basement membrane of the ______________ has been damaged, thus allowing RBC passage into Bowman’s capsular space

glomerulus

What casts are associated with Acute glomerulonephritis and Lupus nephritis

RBC casts

What color are blood casts when stained?

-Unstained are orange-red in color -Stained are deep purple

Red blood cell casts are always observed with...

free-standing RBCs

-Brownish/tan in color -Highly refractive -Best recognized using a polarized light microscope where you can see the maltese cross formation

Fatty casts

What stain is used for Fatty casts?

Sudan III or Oil Red O

What are fatty casts associated with?

When accompanied by massive proteinuria it can be associated with nephrotic syndrome. It is also seen with diabetes mellitus and poisoning from mercury or ethylene glycol

-Lipid-containing RTE cells -Under polarized light they have the maltese cross formation

Oval fat bodies

Oval fat bodies are associated with?

nephrotic syndrome, acute tubular necrosis, diabetes mellitus, trauma cases where bone marrow is released from the long bones.

What are the three liver disease crystals?

-Bilirubin -Leucine -Tyrosine

muddy brown casts and renal tubular epithelial casts were seen in...

acute tubular necrosis -the result of degenerating RBC casts

Urine sediment showing multiple muddy brown granular casts are highly suggestive of ________________ in a patient with acute kidney injury.

acute tubular necrosis

tubular epithelial cells are larger than white cells and have ________________ nucleus.

a single, large central

A baby has urine with a mousy or musty odor and has lighter skin than her siblings. The screening test comes back positive and indicates a disorder in which of the following amino acids? Valine, leucine, isoleucine cystine Tyrosine Phenylalanine

Phenylalanine

Neonatal screening tests are routinely performed for which condition to prevent mental retardation through dietary restrictions?

-Maple Syrup Urine Disease -Phenylketonuria

A patient produces a brown urine and contains the abnormal metabolite homogentisic acid and has areas of dark pigmentation in the eye and ear. This description is consistent with...

Alkaptonuria

A disease that causes large amounts of branched-chain amino acids (valine, leucine, isoleucine) to be excreted in the urine is:

Maple syrup urine disease

A 39 year old woman who is being treated for bipolar disorder comes to the clinic because she has been having issues with frequent urination, and excessive thirst. She explains that she has to wake up a few times each night to urinate. A urinalysis is performed 8 hours after the patient has refrained from liquid intake, and it shows a urine with low specific gravity. What is the likely diagnosis in this patient?

Diabetes insipidus

The presence of “orange sand” in an infant’s diaper is indicative of:

Lesch-Nyhan disease

The common method for analysis of blood samples from newborns is:

Tandem mass spectrometry

Porphyrias result when there is a breakdown in the synthesis of:

Heme

The metabolic disorder that is characterized by the inability to transport cystine and other amino acid across lysosomal membranes resulting in an accumulation in kidney, eye, bone marrow, liver and spleen is? -Cystinuria -Cystinosis -Both cystinuria and cystinosis -neither cystinuria nor cystinosis

Cystinosis

Why is only cystine detected in urine and renal calculi in cystinuria when there are four amino acids (“COLA”) that are not reabsorbed?

Cystine is able to crystalize in the urine and in the formation of calculi

A patient whose urine is port-wine in color and suffering abdominal distress and mental changes can have further testing to detect the presence of ____ in the urine

α-aminolevulinic acid