ASCP MLS Urinalysis and Body Fluids Exam Questions with Correct Verified Answers
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Which is the most common form of porphyria?
A. Erythropoietic porphyria
B. Acute intermittent porphyria
C. Variegate porphyria
D. Porphyria cutanea tarda - ANSWER D. Porphyria is a rare condition, although most of the
inherited forms are autosomal dominant. Porphyria cutanea tarda results from...
ASCP MLS Urinalysis and Body Fluids
Exam Questions with Correct Verified
Answers
Which is the most common form of porphyria?
A. Erythropoietic porphyria
B. Acute intermittent porphyria
C. Variegate porphyria
D. Porphyria cutanea tarda - ANSWER D. Porphyria is a rare condition, although most of the
inherited forms are autosomal dominant. Porphyria cutanea tarda results from a deficiency of
uroporphyrinogen decarboxylase, and hence, the carboxylated forms of uroporphyrin
accumulate in plasma and spill into the urine. The enzyme in hepatocytes is susceptible to
drugs, alcohol, and hepatitis that trigger the disease. The disease usually appears in middle-
aged adults, the majority of whom have hepatitis C infection. The uroporphyrins are highly
fluorescent and may cause port-wine colored urine. Affected persons present with skin
blisters and skin burns if exposed to sunlight.
Which of the following methods is the least sensitive and specific for measuring PBG in urine?
A. Watson-Schwartz test
B. LC-MS
,C. Ion exchange chromatography-Ehrlich's reaction
D. Isotope dilution-MS - ANSWER A. The Watson-Schwartz test is a qualitative screening test for
PBG and is based upon the principle that dietary indole compounds and urobilinogen can be
separated from PBG by extraction. PBG is extracted in n-butanol, while urobilinogen and dietary
indoles are extracted into chloroform. However, the sensitivity and specificity of the test are
poor in comparison to chromatographic and mass spectroscopic methods that better separate
PBG from interfering substances. PBG is elevated in neurological porphyrias, the most common
of which is acute intermittent porphyria.
A brown or black pigment in urine can be caused by:
A. Gantrisin (Pyridium)
B. Phenolsulfonphthalein
C. Rifampin
D. Melanin - ANSWER D. Excretion of melanin in malignant melanoma and homogentisic acid in
alkaptonuria cause the urine to turn black on standing. Other substances that may cause brown
or black-colored urine are methemoglobin, PBG, porphobilin, and urobilin. Gantrisin, PSP dye,
and rifampin are three examples of drugs that cause a red or orange-red color in urine.
Urine that is dark red or port wine in color may be caused by:
A. Lead poisoning
B. Porphyria cutanea tarda
C. Alkaptonuria
D. Hemolytic anemia - ANSWER B. Porphyria cutanea tarda and erythropoietic porphyria
produce sufficient uroporphyrins to cause dark red urine. Acute intermittent porphyria
produces large amounts of PBG, which may be oxidized to porphobilin, turning the urine
orange to orange-brown.
Which of the following tests is affected least by standing or improperly stored urine?
,A. Glucose
B. Protein
C. pH
D. Bilirubin - ANSWER B. Standing urine may become alkaline due to loss of volatile acids and
ammonia production. Bilirubin glucuronides may become hydrolyzed to unconjugated
bilirubin or oxidized to biliverdin, resulting in a false-negative dry reagent strip test. Glucose
can be consumed by glycolysis or oxidation by cells.
Which type of urine sample is needed for a D-xylose absorption test on an adult patient?
A. 24-hour urine sample collected with 20 mL of 6 N HCl
B. 2-hour timed postprandial urine preserved with boric acid
C. 5-hour timed urine kept under refrigeration
D. Random urine preserved with formalin - ANSWER C. The D-xylose absorption test is used to
distinguish pancreatic insufficiency from intestinal malabsorption. The test requires a blood
sample taken 2 hours after oral administration of 25 g of D-xylose, and a 5-hour timed urine
sample. D-xylose is absorbed without the aid of pancreatic enzymes, and is not metabolized by
the liver. Therefore, deficient absorption (denoted by a plasma level < 25 mg/dL and urine
excretion of <4g/5hours) points to malabsorption syndrome. Tests requiring a 24-hour urine
sample include catecholamines, vanillylmandelic acid (VMA), metanephrines, cortisol, and
estriol.
Which of the following is inappropriate when collecting a 24-hour urine sample for
catecholamines?
A. Urine in the bladder is voided and discarded at the start of the test
B. At 24 hours, any urine in the bladder is voided and added to the collection
C. All urine should be collected in a single container that is kept refrigerated
, D. Ten mL of 1N sodium hydroxide should be added to the container before collection -
ANSWER D. When collecting a 24-hour urine sample, the bladder must be emptied of urine at
the start of the test and discarded. The bladder must be emptied at the conclusion of the test
and the urine added to the collection. In order to prevent degradation of catecholamines
VMA, metanephrines, and cortisol, the urine must be refrigerated during storage and kept at
2°C-8°C until analysis or frozen. If the pH of the specimen exceeds 3.0, degradation of
catecholamines can occur. Preservation of the urine with acid is no longer required for VMA,
metanephrines and cortisol.
Urine production of less than 400 mL/day is:
A. Consistent with normal renal function and H2O balance
B. Termed isosthenuria
C. Defined as oliguria
D. Associated with diabetes mellitus - ANSWER C. Normal daily urine excretion is usually 600-
1,600 mL/day. Isosthenuria refers to urine of constant specific gravity (SG) of 1.010, which is
the SG of the glomerular filtrate. Glycosuria causes retention of H2O within the tubule,
resulting in dehydration and polyuria rather than oliguria.
Which of the following contributes to SG, but not to osmolality?
A. Protein
B. Salt
C. Urea
D. Glucose - ANSWER A. All substances that dissolve in the urine contribute to osmotic pressure
or osmolality. This includes nonionized solutes such as urea, uric acid, and glucose as well as
salts, but not colloids such as protein and lipids.
Urine with an SG consistently between 1.002 and 1.003 indicates:
A. Acute glomerulonephritis
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