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*** Clinical Chemistry 8th > Nonprotein Nitrogen Compounds > Flashcards

Nonprotein Nitrogen Compounds Flashcards

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1
Q

. Which one of the following is not an NPN substance?
a. Allantoin
b. Ammonia
c. Creatinine
d. Urea

A

b. Ammonia

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2
Q

Which compound constitutes nearly half of the NPN substances in the blood?
a. Ammonia
b. Creatine
c. Urea
d. Uric acid

A

c. Urea

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3
Q

A technologist reports urea N of 9 mg/dL. What is the urea concentration for
this sample?
a. 3.2 mg/dL
b. 4.2 mg/dL
c. 18.0 mg/dL
d. 19.3 mg/dL

A

d. 19.3 mg/dL

  • The molecular weight of urea (CO(NH2)2) is 60 g/mol, and the molecular weight of nitrogen (N) is 14 g/mol.

-The proportion of nitrogen in urea is (2 * 14) / 60 = 28 / 60 = 0.4667

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4
Q

Which blood collection tube additive can be used to collect a specimen for
measurement of urea?
a. Ammonium
b. Lithium heparin
c. Sodium citrate
d. Sodium fluoride

A

b. Lithium heparin

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5
Q

In the clinical laboratory, urea N is measured most often using
a. Conductivity
b. Enzymatic reactions
c. Isotope dilution mass spectrometry
d. Multilayer film formats

A

b. Enzymatic reactions

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6
Q

Elevated blood urea concentration is termed
a. Azotemia
b. BUN
c. Uremia
d. Uremic syndrome

A

a. Azotemia

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7
Q

Prerenal azotemia is caused by
a. Acute renal failure
b. Chronic renal failure
c. Congestive heart failure
d. Urinary tract obstruction

A

c. Congestive heart failure

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8
Q

A technologist obtains a urea N value of 61 mg/dL ( 3.3 mmol/L) and a serum creatinine
value of 2.5 mg/dL (0.139 mmol/L) on a patient. These results indicate
a. Congestive heart failure
b. Dehydration
c. Glomerular nephritis
d. Urinary tract obstruction

A

d. Urinary tract obstruction

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9
Q

Uric acid is the final product of
a. Allantoin metabolism
b. Amino acid metabolism
c. Purine metabolism
d. The urea cycle

A

c. Purine metabolism

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10
Q

Sources of error in measurement of uric acid include
a. Assay interference
b. Competition from alternate purine substrates
c. Narrow spectrophotometer bandwidth
d. Nonspecific enzyme activity

A

a. Assay interference
b. Competition from alternate purine substrates
c. Narrow spectrophotometer bandwidth
d. Nonspecific enzyme activity

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11
Q

Which condition is not associated with elevated plasma uric acid
concentration?
a. Allopurinol overtreatment
b. Gout
c. Lesch-Nyhan syndrome
d. Renal disease

A

a. Allopurinol overtreatment

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12
Q

Complete deficiency of hypoxanthine–guanine phosphoribosyltransferase
results in which disease?
a. Allantoinism
b. Glycogen storage disease
c. Lesch-Nyhan syndrome
d. Megaloblastic anemia

A

c. Lesch-Nyhan syndrome

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13
Q

Uric acid nephrolithiasis refers to
a. Acidification of the urine to dissolve renal calculi
b. Formation of renal calculi composed of uric acid
c. Precipitation of urates in the urinary tract
d. Saturation of the kidney with uric acid

A

b. Formation of renal calculi composed of uric acid

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14
Q

A 45-year-old male presents to the emergency department complaining of
intense joint pain. The previous night the patient experienced similar pain
accompanied by inflammation and redness of his wrists and large toe. The
physician on-call orders testing for serum uric acid concentration. Which
laboratory results and diagnosis are consistent with the physician’s
assessment? The reference interval for uric acid is 3.5 to 7.2 mg/dL.
a. Uric acid 1.9 mg/dL; Fanconi syndrome
b. Uric acid 1.0 mg/dL; hereditary xanthinuria
c. Uric acid 9.1 mg/dL; alcoholism
d. Uric acid 9.1 mg/dL; gout

A

d. Uric acid 9.1 mg/dL; gout

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15
Q

Which statement describes creatinine biosynthesis accurately?
a. Creatine is phosphorylated in the liver to form phosphocreatinine.
b. Creatine phosphate undergoes spontaneous cyclization to form
creatinine.
c. Creatinine is formed from creatine and creatine phosphate in the liver.
d. Creatinine is synthesized from arginine, glycine, and methionine in the
liver.

A

d. Creatinine is synthesized from arginine, glycine, and methionine in the
liver.

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16
Q

Substances known to increase results when measuring creatinine by the Jaffe
reaction include all of the following EXCEPT
a. Ascorbic acid
b. Bilirubin
c. Glucose
d. α-Keto acids

A

B.Bilirubin

17
Q

. In the Jaffe reaction, a red-orange chromogen is formed when creatinine
reacts with
a. Aluminum magnesium silicate
b. Creatininase
c. Phosphocreatine
d. Picric acid

A

d. Picric acid

18
Q

Creatinine excretion typically
a. Decreases from childhood to middle age
b. Does not vary with age and sex
c. Is higher for females than for males
d. Is highest for adult men aged 18 to 50 years

A

d. Is highest for adult men aged 18 to 50 years

19
Q

Use of serum creatinine to calculate GFR
a. Is discouraged because the calculations are complex
b. Is encouraged as a means to identify kidney disease and improve
patient care
c. Requires hospitalization of the patient for specimen collection
d. Requires simultaneous measurement of creatinine in a 24-hour urine
collection

A

b. Is encouraged as a means to identify kidney disease and improve
patient care

20
Q

Which factor must be considered for calculation of creatinine clearance using
the MDRD equation?
a. Certification of body mass index
b. Documentation of specimen collection time
c. Identification of ethnicity
d. Verification that the patient was fasting

A

c. Identification of ethnicity

21
Q

Which situation would be expected to falsely increase measured blood
ammonia concentration?
a. The patient smoked two cigarettes 15 minutes prior to phlebotomy.
b. The patient was fasting for 8 hours before blood collection.
c. The patient ate a steak dinner the night before the specimen was
collected.
d. The specimen was placed on ice immediately after collection

A

a. The patient smoked two cigarettes 15 minutes prior to phlebotomy

22
Q

Although arterial blood is the recommended specimen for determination of
this analyte, it is seldom used.
a. Ammonia
b. Creatine
c. Urea
d. Uric acid

A

a. Ammonia

23
Q

Toxic effects of elevated blood ammonia concentration include
a. Decreased renal function
b. Hemorrhage and dehydration
c. Mental status changes and coma
d. Pain and inflammation of peripheral joints

A

c. Mental status changes and coma

24
Q

Ammonia concentrations are measured to evaluate
a. Acid–base status
b. Glomerular filtration
c. Hepatic encephalopathy
d. Renal failure

A

c. Hepatic encephalopathy

25
Q

Ammonia concentration correlates with disease severity and prognosis for
a. Astrocytosis
b. Inherited deficiencies of urea cycle enzymes
c. Neurological deterioration
d. Reye’s syndrome

A

b. Inherited deficiencies of urea cycle enzymes

*** Clinical Chemistry 8th (34 decks)

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