(26) RA VICTORINO Flashcards
Which one of the following is not an NPN substance?
a. Allantoin
b. Ammonia
c. Creatinine
d. Urea
a. Allantoin
Which compound constitutes nearly half of the NPN substances in the blood?
a. Ammonia
b. Creatine
c. Urea
d. Uric acid
c. Urea
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
d. 19.3 mg/dL
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
b. Lithium heparin
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
b. Enzymatic reactions
Elevated blood urea concentration is termed
a. Azotemia
b. BUN
c. Uremia
d. Uremic syndrome
a. Azotemia
Prerenal azotemia is caused by
a. Acute renal failure
b. Chronic renal failure
c. Congestive heart failure
d. Urinary tract obstruction
c. Congestive heart failure
A technologist obtains a urea N value of 61 mg/dL and a serum creatinine
value of 2.5 mg/dL on a patient. These results indicate
a. Congestive heart failure
b. Dehydration
c. Glomerular nephritis
d. Urinary tract obstruction
d. Urinary tract obstruction
Uric acid is the final product of
a. Allantoin metabolism
b. Amino acid metabolism
c. Purine metabolism
d. The urea cycle
c. Purine metabolism
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. Assay interference
Which condition is not associated with elevated plasma uric acid
concentration?
a. Allopurinol overtreatment
b. Gout
c. Lesch-Nyhan syndrome
d. Renal disease
a. Allopurinol overtreatment
Complete deficiency of hypoxanthine–guanine phosphoribosyltransferase
results in which disease?
a. Allantoinism
b. Glycogen storage disease
c. Lesch-Nyhan syndrome
d. Megaloblastic anemia
c. Lesch-Nyhan syndrome
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
b. Formation of renal calculi composed of uric acid
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
d. Uric acid 9.1 mg/dL; gout
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.
c. Creatinine is formed from creatine and creatine
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
b. Bilirubin
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
d. Picric acid
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
d. Is highest for adult men aged 18 to 50 years
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
b. Is encouraged as a means to identify kidney disease and improve
patient care
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
c. Identification of ethnicity
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.
a. The patient smoked two cigarettes 15 minutes prior to phlebotomy.
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. Ammonia
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. Decreased renal function
Ammonia concentrations are measured to evaluate
a. Acid–base status
b. Glomerular filtration
c. Hepatic encephalopathy
d. Renal failure
c. Hepatic encephalopathy
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
b. Inherited deficiencies of urea cycle enzymes
- The NPN compound present in highest concentration in the blood
- major excretory product of protein metabolism.
urea
Following synthesis in the
___, urea is carried in the blood to the ___, where it is readily filtered from
the plasma by the ___.
Following synthesis in the
liver, urea is carried in the blood to the kidney, where it is readily filtered from
the plasma by the glomerulus.
Measurement of urea is used to evaluate
- renal function,
- to assess hydration
status, - to determine nitrogen balance,
- to aid in the diagnosis of renal disease, and
- to verify adequacy of dialysis
catalyzes hydrolysis of urea in the sample
urease (urea
amidohydrolase
used to refer to urea determination.
Blood Urea Nitrogen (BUN)
elevated conc. of urea in blood
Azotemia
Very high plasma urea concentration accompanied by renal failure is called
uremia, or the uremic syndrome
Reference range of Urea N:
Serum or plasma: 6-20 mg/dl
24 hours Urine: 12-20 g/day
produced as a waste product of creatine and creatine phosphate.
creatinine
measure of the amount of creatinine eliminated from the blood by the kidneys per unit time
Creatinine Clearance
final breakdown product of purine metabolism (adenosine/guanine) in liver
uric acid
Comes from deamination of amino acids
ammonia
Reference Method
Isotope Dilution Mass Spectrometry
urea site of formation
liver
decreased BUN
- Low protein intake,
- Severe vomiting and diarrhea,
- Liver disease and
- Pregnancy
Creatine First Transamidation:
Arginine and Glycine
Creatine Second Reaction:
Methionine
increased creatine
- Muscular dystrophy,
- Poliomyelitis,
- Hyperthyroidism and
- Trauma
reliable test for renal function because it is relatively independent to protein diet, hydration and protein metabolism
serum creatinine
Normal Urea Nitrogen/ Creatinine Ratio
10:1 – 20:1
Gold standard for Glomerular Filtration Rate
Inulin (best exogenous substance)
- indirect method to assess GFR
- mL of cleared plasma creatinine by kidneys per minute
Clearance
uric acid in plasma
monosodium urate
