Exam II Flashcards
How does the pH of urine relate to its hydrogen ion concentration?
inversely; the higher the number of ions, the lower the pH
Ketone bodies in the urine are suggestive of the elevated metabolism of what substance?
fat
What causes myoglobinuria?
usually rhabdomyolysis (muscle destruction); can also be caused by trauma, venoms, and certain drugs
What is the general purpose of test strip screening?
provides immediate answers as to whether or not pathological concentrations of substances are present in the urine, which can determine if further clinical testing is necessary to confirm a diagnosis suggested by the screen
What color is a positive nitrite reading on a dipstick?
any degree of uniform pink color
What substance is most likely to be present in urine that could cause a false negative reaction for glucose on a dipstick?
ascorbic acid (vitamin C)
What is sulfosalicylic acid (SSA) used for?
detecting urinary proteins, especially Bence-Jones proteins or immunoglobulin light chains, which cannot be detected with dipsticks
What test is used for detecting reducing sugars in urine, and what would the microscopic correlation be expected to show?
Clinitest; nothing would show on the microscopic exam
What two dipstick reactions are usually positive in pyelonephritis and cystitis?
leukocytes and nitrites
What conditions could be indicated by an elevated urinary urobilinogen?
liver disease (cirrhosis, hepatitis), hemolytic states (hemolytic anemia, pernicious anemia)
What conditions can cause hemoglobinuria?
intravascular hemolysis (transfusion reactions, hemolytic anemia, paroxysmal nocturnal hemoglobinuria [PNH]), extensive burns, infections (malaria, Clostridium perfringens, syphilis, Mycoplasma pneumoniae), chemical toxicity, exercise
What is specificity in regards to dipstick reactions?
each test zone should react specifically to the substance being tested for and no other
What does the test pad for ketone bodies detect?
acetoacetic acid
What is the principle of the dipstick method for protein?
protein error of indicators - ability of protein to alter the color of some acid-base indicators without altering the pH
What unusual protein is associated with multiple myeloma?
Bence-Jones (present in ~50% of cases)
What sugar, especially in infants, is most likely indicated by a negative dipstick reaction for glucose and a positive Clinitest?
galactose
What specimen is used to detect orthostatic proteinuria, and when would you suspect this condition?
first morning specimen; urinary protein is excreted when the patient is erect but not when lying down, and without apparent disease (usually in children and adolescents)
What is the active ingredient in Ehrlich’s reagent?
p-dimethylaminobenzaldehyde (DMAB)
What is the reagent used to detect bilirubin in the Ictotest?
2,4-dichlorobenzenediazonium tetrachlorozincate
What does the reagent pad for hemoglobin detect?
hemoglobin, myoglobin, and erythrocytes
What is the action of the enzyme peroxidase?
pseudoperoxidase activity
Why is there normally no glucose in the urine?
the glomerulus usually filters out glucose, where it is completely reabsorbed into the blood by the proximal convoluted tubules
What is the advantage of using phase contrast microscopy in the examination of urinary sediment, and how does this relate to the refractive index?
permits more detailed visualization of translucent or low-refractive components and living cells by using a special condenser to convert variations in refractive index into variations in contrast (unstained cellular components and casts; mucus and casts have an index similar to that of urine
What is the use of a polarizing microscope in urinalysis?
it detects birefringent (anisotropic) sediment; most often used to confirm the presence of fat, especially cholesterol (Maltese cross formation); also distinguishes calcium oxalate from red cells, waxy casts from fibers, and amorphous from coccoid bacteria
How are cell numbers recorded and what objective is used?
cells/high power field (40-45x)
How many fields should be examined in a manual microscopic examination?
10
What is the most common type of white cell found in urinary sediment?
neutrophils
Casts in urine are usually accompanied by a positive test for what?
protein
Casts containing cells usually indicate a problem in what part of the urinary tract?
kidneys
Where are transitional epithelial cells found?
renal calyces, renal pelvis, ureters, bladder, and ~2/3 of the male urethra
Amorphous phosphates are found in urine of what pH?
alkaline
What disease is indicated when tyrosine and leucine are found in the urine?
aminoacidemia, and occasionally in severe liver disease
What two kinds of urine characterize nephrotic syndrome?
proteinuria and lipiduria
What kind of casts have at least two distinct components?
mixed casts
How are cast numbers recorded and which objective should be used?
of casts/low power field (10x)
Which white cell is likely to be found in a transplant rejection?
lymphocytes
In what specific portions of the nephron are casts formed?
distal and collecting tubules (lumen)
In what general type of diseases or red cell casts found?
intrinsic renal disease (damage to the basement membrane of the glomerulus)
What specific type of epithelial cells are found in epithelial cell casts?
renal tubular epithelial cells
Glitter cells are associated with urine of what specific gravity?
low
What type of epithelial cells are indicative of vaginal contamination?
squamous epithelial cells
Calcium oxalate crystals are normally found in urine of what pH?
acidic
What condition is indicated by large numbers of uric acid crystals?
gout
Candida albicans is often found in the urine of patients with what two conditions?
diabetes mellitus, or systemic yeast infection
If flat, hexagonal, colorless crystals are found in the urine, what constituent is suggested; and what should be done before these crystals are reported?
cystine crystals; confirmation using the cyanide-nitroprusside reaction test
How can red cells and yeast be differentiated?
yeast will not lyse in acetic acid, nor will it stain with supravital stains, whereas red cells will; yeast is also more refractile, and size can vary considerably within the same specimen
What is the appearance of waxy casts?
high refractive index; sharp, blunt, or uneven ends; homogenous, irregular shape; characteristic cracks or fissures on lateral margins or along the axes
What organisms can indicate contamination if found in the urine?
bacteria (especially Gram-negative), yeast (usually Candida albicans), sperm, Trichomonas vaginalis, Gardnerella vaginalis, parasites/ova (pinworm or blood/bladder fluke)
What is the order for the aging process of casts?
cellular, coarse granular, fine granular, waxy
What is the term for the presence of elevated numbers of casts in urine?
cylinduria
How can a precipitate of amorphous phosphates be removed?
they are soluble in dilute acetic acid
How can a precipitate of amorphous urates be removed?
they can be dissolved in alkali or by heating to ~60*C with warm saline
Can Multistix be used to detect a negative urobilinogen?
no; they only have a sensitivity of 0.2
How would a negative nitrite alongside a positive bacteria be interpreted?
urinary tract infection caused by bacteria that do not have the ability to convert nitrates to nitrites; urine has not been in the bladder long enough for conversion; dietary nitrates are absent; bacterial population is so high that they reduce nitrates to N2; increased specific gravity; antibiotic therapy; ascorbic acid is present (can cause a false negative)
How would red cells appear in hypertonic urine?
crenated
What happens if the dipstick is dipped too many times?
reagents on the individual pads may start to run together
What type of cast may be found in urine of normal pH?
hyaline
What are shadow cells?
red cells that swell in hypotonic solution, release their hemoglobin, and appear as colorless, empty circles; also called ghost cells
What is the significance of the size and shape of a cast?
the degree of damage done to the renal tubules; clues to cast identification
At what temperature should urine used for testing be?
room temperature
Why is the refractometer used for specific gravity rather than the dipstick?
requires a small sample size; auto-compensates for specimens between 15-37*C; calibrated for both specific gravity and protein determinations; can be used with both ionic and non-ionic solutes (dipsticks can only use ionic)
How does the Watson-Schwartz test differentiate between urobilinogen and prophobilinogen?
modified Ehrlich’s test based on the different solubility characteristics of prophobilinogen and urobilinogen with regard to pH and solvent type; urobilinogen is soluble in chloroform and butinol, porphobilinogen remains in the aqueous layer
What is the principle of the automated instruments for dipstick reading?
utilize reflectance photometry method - when light strikes reagent pad, some light is absorbed and the remaining light is scattered; it is performed at a specific wavelength depending on the color of the reagent pad
What two terms are used to refer to glucose in the urine?
glucosuria, glycosuria
What are the two different forms of blood in the urine described as?
hematuria (red cells) and hemoglobinuria
What reagent is used to differentiate between precipitated urinary hemoglobin and myoglobin?
ammonium sulfate
What is the normal range for urinary urobilinogen?
What test is the most sensitive for bilirubin?
Ictotest
What is ketonuria?
presence of ketone bodies in the urine
What are the two equations for the detection of glucose?
glucose + O2 —glucose oxidase–> gluconic acid + H2O2, and H2O2 + chromagen —peroxidase–> oxidized chromogen + H2O
What reagent is used to detect ketones?
sodium nitroprusside
What reagent is used to detect urobilinogen?
p-dimethylaminobenzaldehyde
What reagent is used to detect protein?
tetrabromphenol blue
What reagent is used to detect pH?
bromthymol blue, methyl red
What reagent is used to detect nitrites?
1,2,3,4-tetrahydrobenzo(h)quinolin-3-ol
What reagent is used to detect bilirubin?
2,4-dichloroaniline diazonium salt
What reagents are used to detect glucose?
glucose oxidase, horseradish peroxidase, potassium iodide
What reagent is used to detect blood?
3,3’,5,5’-tetramethylbenzidine
