Creatinine, Uric Acid, BUN, Ammonia

Question 1

Creatinine is formed from the:
A. Oxidation of creatine
B. Oxidation of protein
C. Deamination of dibasic amino acids
D. Metabolism of purines

Answer 1

A

Question 2

Creatinine is considered the substance of choice to
measure endogenous renal clearance because:
A. The rate of formation per day is independent of
body size
B. It is completely filtered by the glomeruli
C. Plasma levels are highly dependent upon diet
D. Clearance is the same for both men and women

Answer 2

B

Question 3

Which statement regarding creatinine is true?
A. Serum levels are elevated in early renal disease
B. High serum levels result from reduced
glomerular filtration
C. Serum creatine has the same diagnostic utility as
serum creatinine
D. Serum creatinine is a more sensitive measure of
renal function than creatinine clearance

Answer 3

B

Question 4

Which of the following formulas is the correct
expression for creatinine clearance?
A. Creatinine clearance = U/P X V X 1.73/A
B. Creatinine clearance = P/V X U X A/1.73
C. Creatinine clearance = P/V X U X 1.73/A
D. Creatinine clearance = U/V X P X 1.73/A

Answer 4

A

Question 5

Which of the following conditions is most likely to
cause a falsely high creatinine clearance result?
A. The patient uses the midstream void procedure
when collecting his or her urine
B. The patient adds tap water to the urine container
because he or she forgets to save one of the urine
samples
C. The patient does not empty his or her bladder at
the conclusion of the test
D. The patient empties his or her bladder at the start of the test and adds the urine to the collection

Answer 5

D

Question 6

The modification of diet in renal disease (MDRD)
formula for calculating eGFR requires which four
parameters?
A. Urine creatinine, serum creatinine, height,
weight
B. Serum creatinine, age, gender, race
C. Serum creatinine, height, weight, age
D. Urine creatinine, gender, weight, age

Answer 6

B

Question 7

What substance may be measured as an alternative
to creatinine for evaluating GFR?
A. Plasma urea
B. Cystatin C
C. Uric acid
D. Potassium

Answer 7

B

Question 8

Which of the following enzymes allows creatinine
to be measured by coupling the creatinine
amidohydrolase (creatininase) reaction to the
peroxidase reaction?
A. Glucose-6-phosphate dehydrogenase
B. Creatinine iminohydrolase
C. Sarcosine oxidase
D. Creatine kinase

Answer 8

C

Question 9

Select the primary reagent used in the Jaffe
method for creatinine.
A. Alkaline copper II sulfate
B. Saturated picric acid and NaOH
C. Sodium nitroprusside and phenol
D. Phosphotungstic acid

Answer 9

B

Question 10

Interference from other reducing substances can be
partially eliminated in the Jaffe reaction by:
A. Measuring the product at 340 nm
B. Measuring the product with an electrode
C. Measuring the timed rate of product formation
D. Performing a sample blank

Answer 10

C

Question 11

Which of the following statements is true?
A. Cystatin C is measured immunochemically
B. The calibrator used for cystatin C is traceable to
the National Bureau of Standards calibrator
C. Cystatin C assays have a lower coefficient of
variation than plasma creatinine
D. Enzymatic and rate Jaffe reactions for creatinine
give comparable results

Answer 11

A

Question 12

In which case would eGFR derived from the
plasma creatinine likely give a more accurate
measure of GFR than measurement of plasma
cystatin C?
A. Diabetic patient
B. Chronic renal failure
C. Post–renal transplant
D. Chronic hepatitis

Answer 12

C

Question 13

A sample of amniotic fluid collected for fetal lung
maturity studies from a woman with a pregnancy
compromised by hemolytic disease of the newborn
(HDN) has a creatinine of 88 mg/dL. What is the
most likely cause of this result?
A. The specimen is contaminated with blood
B. Bilirubin has interfered with the measurement of
creatinine
C. A random error occurred when the absorbance
signal was being processed by the analyzer
D. The fluid is urine from accidental puncture of
the urinary bladder

Answer 13

D

Question 14

Which analyte should be reported as a ratio using
creatinine concentration as a reference?
A. Urinary microalbumin
B. Urinary estriol
C. Urinary sodium
D. Urinary urea

Answer 14

A

Question 15

Urea is produced from:
A. The catabolism of proteins and amino acids
B. Oxidation of purines
C. Oxidation of pyrimidines
D. The breakdown of complex carbohydrates

Answer 15

A

Question 16

Urea concentration is calculated from the BUN by
multiplying by a factor of:
A. 0.5
B. 2.14
C. 6.45
D. 14

Answer 16

B

Question 17

Which of the statements below about serum urea
is true?
A. Levels are independent of diet
B. Urea is not reabsorbed by the renal tubules
C. High BUN levels can result from necrotic liver
disease
D. BUN is elevated in prerenal as well as renal
failure

Answer 17

D

Question 18

A patient’s BUN is 60 mg/dL and serum
creatinine is 3.0 mg/dL. These results suggest:
A. Laboratory error measuring BUN
B. Renal failure
C. Prerenal failure
D. Patient was not fasting

Answer 18

C

Question 19

Urinary urea measurements may be used for
calculation of:
A. Glomerular filtration
B. Renal blood flow
C. Nitrogen balance
D. All of these options

Answer 19

C

Question 20

BUN is determined electrochemically by coupling
the urease reaction to measurement of:
A. Potential with a urea-selective electrode
B. The timed rate of increase in conductivity
C. The oxidation of ammonia
D. Carbon dioxide

Answer 20

B

Question 21

In the ultraviolet enzymatic method for BUN, the
urease reaction is coupled to a second enzymatic
reaction using:
A. AST
B. Glutamate dehydrogenase
C. Glutamine synthetase
D. Alanine aminotransferase (ALT)

Answer 21

B

Question 22

Which product is measured in the coupling step of
the urease-UV method for BUN?
A. CO2
B. Dinitrophenylhydrazine
C. Diphenylcarbazone
D. NAD+

Answer 22

D

Question 23

Which enzyme deficiency is responsible for
phenylketonuria (PKU)?
A. Phenylalanine hydroxylase
B. Tyrosine transaminase
C. p-Hydroxyphenylpyruvic acid oxidase
D. Homogentisic acid oxidase

Answer 23

A

Question 24

Which of the following conditions is classified as a
renal-type aminoaciduria?
A. Fanconi syndrome
B. Wilson’s disease
C. Hepatitis
D. Homocystinuria

Answer 24

A

Question 25

Which aminoaciduria results in the overflow of
branched chain amino acids?
A. Hartnup’s disease
B. Alkaptonuria
C. Homocystinuria
D. Maple syrup urine disease

Answer 25

D

Question 26

In addition to phenylketonuria, maple syrup
urine disease, and homocystinuria, what other
aminoaciduria can be detected by tandem MS?
A. Alkaptonuria
B. Hartnup disease
C. Citrullinemia
D. Cystinuria

Answer 26

C

Question 27

Of the methods used to measure amino acids,
which is capable of measuring fatty acids
simultaneously?
A. Tandem-mass spectroscopy
B. High-performance liquid chromatography
C. Capillary electrophoresis
D. Two-dimensional thin-layer chromatography

Answer 27

A

Question 28

Blood ammonia levels are usually measured in
order to evaluate:
A. Renal failure
B. Acid–base status
C. Hepatic coma
D. Gastrointestinal malabsorption

Answer 28

C

Question 29

Which statement about ammonia is true?
A. Normally, most of the plasma ammonia is
derived from peripheral blood deamination of
amino acids
B. Ammonia-induced coma can result from
salicylate poisoning
C. Hepatic coma can result from Reye’s syndrome
D. High plasma ammonia is usually caused by
respiratory alkalosis

Answer 29

C

Question 30

Uric acid is derived from the:
A. Oxidation of proteins
B. Catabolism of purines
C. Oxidation of pyrimidines
D. Reduction of catecholamines

Answer 30

B

Question 31

Which of the following conditions is associated
with hyperuricemia?
A. Renal failure
B. Chronic liver disease
C. Xanthine oxidase deficiency
D. Paget’s disease of the bone

Answer 31

A

Question 32

Orders for uric acid are legitimate stat requests
because:
A. Levels above 10 mg/dL cause urinary tract calculi
B. Uric acid is hepatotoxic
C. High levels induce aplastic anemia
D. High levels cause joint pain

Answer 32

A

Question 33

Which uric acid method is associated with
negative bias caused by reducing agents?
A. Uricase coupled to the Trinder reaction
B. Ultraviolet uricase reaction coupled to catalase
and alcohol dehydrogenase reactions
C. Measurement of the rate of absorbance decrease at 290 nm after addition of uricase
D. Phosphotungstic acid using a protein-free filtrate

Answer 33

A