Exam II Flashcards
(78 cards)
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
