U2.3 NPN : Urea [L] Flashcards
1
Q
Nitrogen-containing compounds measured after removal of proteins in specimen
A
Non-Protein Nitrogen
2
Q
Non-Protein Nitrogen is measured by converting _____ to _______
A
converting nitrogen to ammonia
3
Q
reagent used to convert nitrogen to ammonia
A
Nessler’s reagent
4
Q
product measured spectrophotometrically (color)
A
yellow product
5
Q
Measured by converting nitrogen to ammonia and subsequent reaction with Nessler’s reagent (K2[Hgl4]) to form a yellow product measured spectrophotometrically
A
Non-Protein Nitrogen
6
Q
Select: Part of Non-Protein Nitrogen (NPN)
A. Urea
B. Creatinine
C. Glucose
D. Uric Acid
A
A B D
7
Q
In urine, __________ contributes 4.5% of excreted nitrogen, while __________ contributes 1.7%.
A
Creatinine, Uric Acid
8
Q
% of total Urea in Plasma
A
45-50
9
Q
% of Urea in urine Concentration
A
86
10
Q
Specimens used for Urea Determination
A
serum, urine & plasma
11
Q
Also known as carbamide
A
Urea
12
Q
Highest concentration in blood
A
Urea
13
Q
Urea is produced in the _____ from amino groups (-NH2) and free ammonia
A
liver
14
Q
Major excretory product of protein metabolism
A
Urea
15
Q
Chemical formula of Urea
A
CO(NH2)2
16
Q
T/F Clinical application of urea include evaluation of renal function
A
T
17
Q
T/F Clinical application of urea includes assessing hydration status
A
T
18
Q
T/F Clinical application of urea include determination of nitrogen balance
A
T
19
Q
T/F Clinical application of urea include aid in the diagnosis of liver disease
A
F renal
20
Q
T/F Clinical application of urea include verify adequacy of dialysis
A
T
21
Q
Select: Clinical applications of Urea testing
A. Evaluation of renal function
B. Determination of blood glucose levels
C. Assessing hydration status
D. Verifying adequacy of dialysis
A
A C D
22
Q
More appropriate term for quantification of urea
A
Blood Urea Nitrogen (BUN) Determination
23
Q
BUN Determination
Conversion factor (mg/dL to mmol/L):
A
x 0.357
24
Q
BUN Determination
BUN to Urea
A
Urea = BUN x 2.14
25
BUN Determination
Urea to BUN
BUN = Urea / 2.14
26
BUN Determination
Most frequently used method
ENZYMATIC METHOD
27
BUN Determination
Uses urease enzyme to catalyze hydrolysis of urea and the liberated ammonium ion (NH4+) is quantified.
ENZYMATIC METHOD
28
T/F the most frequently used method for BUN determination is the enzymatic method which uses the urease enzyme
t
29
BUN Determination
enzyme used to catalyze hydrolysis of urea and the liberated ammonium ion (NH4+) is quantified
urease
30
BUN Determination : Enzymatic Method
most common assay
Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
31
Select: Indicator Dye Method commonly used in the following systems
A. Automated Systems
B. Dry Reagent Strips
C. Spectrophotometers
D. Multilayer Film Reagents
A B D
32
BUN Determination : Enzymatic Method
best as a kinetic measurement
Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
33
T/F GLDH-coupled enzymatic reaction is best used for static measurements
F - best used as kinetic measurement
34
BUN Determination : Enzymatic Method
measures rate of disappearance of nicotinamide adenine dinucleotide (reduced NADH) at 340 nm
Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
35
GLDH coupled reaction for BUN determination measures the rate of disappearance of __________ at 340 nm.
NADH (reduced nicotinamide adenine dinucleotide)
36
BUN Determination : Enzymatic Method
wavelength that measures rate of disappearance of nicotinamide adenine didnucleotide (reduced NADH)
340 nm
37
T/F more ammonium ions result in a faster reduction of NADH to NAD+ in GLDH reaction
T
38
BUN Determination : Enzymatic Method
used in automated systems, multilayer film reagents and dry reagent strips
Indicator dye
39
BUN Determination : Enzymatic Method
measures color change due to change in pH
Indicator dye
40
BUN Determination : Enzymatic Method
a specific and rapid test
Conductometric
41
BUN Determination : Enzymatic Method
uses electrode to measure rate of increase in conductivity produced by ammonium ions
Conductometric
42
BUN Determination
reference method
ISOTOPE DILUTION MASS SPECTROMETRY (IDMS)
43
BUN Determination
uses isotopically-labeled compound for quantification
ISOTOPE DILUTION MASS SPECTROMETRY (IDMS)
44
BUN Determination
detects characteristic fragments following ionization
ISOTOPE DILUTION MASS SPECTROMETRY (IDMS)
45
Specimen considerations for Urea Determination
Sample: Serum, plasma or urine
46
Odd One Out: Sample for BUN
A. Serum
B. Plasma
C. Urine
D. Saliva
D
*B - lithium heparinized plasma
47
Select: Blood Urea Nitrogen (BUN) determination - Enzymatic method
A. Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
B. Colorimetric analysis
C. Conductometric
D. Isotope Dilution Mass Spectrometry (IDMS)
A C
48
Tops that are not allowed for Urea Determination
Light Blue - sodium citrate
Grey - sodium fluoride
49
Select All That Apply: Avoided or considered for urea determination,,
A. Using citrate as an anticoagulant
B. Using fluoride as an anticoagulant
C. Using hemolyzed samples
D. Processing the sample immediately or refrigerating it
A B C
50
if urine samples are not processed within a few hours, they should be __________ to prevent bacterial consumption of urea
refrigerated
51
dilution factor commonly used when diluting urine samples with normal saline for urea concentration analysis
1:20
51
Select: Materials for urea determination
A. Serological pipet
B. Rubber aspirators
C. Ellitrol I (Normal Control)
D. Centrifuge
E. Spectrophotometer
A, B, C, D, E
52
Urea Reagent Kit; Reagent 1
R1 Tris buffer (pH 7.6), ADP, α-ketoglutarate, urease, glutamate dehydrogenase, sodium azide
53
Urea Reagent Kit; Reagent 2
NADH, sodium azide (irritates eyes and skin)
54
T/F Sodium azide, present in both reagents, is safe and does not irritate the eyes or skin
F - sod azide irritates eyes and skin
55
standard urea concentration is __________ mg/dL or _____ mmol/L, though this may vary depending on the manufacturer
50; 8.33
56
Select: Materials for BUN Enzymatic Reaction
A. Serologic pipet
B. Hemocytometer
C. Spectrophotometer
D. Centrifuge
A C D
57
in the BUN determination procedure, the sample volume is delivered by touching the tip of the pipet to the __________ of the tube
bottom
58
T/F the working reagent is prepared by mixing 1 volume of reagent 1 with 2 volumes of reagent 2
F - 1 volume of Reagent 2
59
T/F working reagent for urea determination should be prepared ahead of time before starting the analysis
F - only when starting analysis
60
BUN Determination Procedure
Feed the solution in the machine at __ seconds for A1
27 seconds
61
BUN Determination Procedure
Feed the solution in the machine at __ seconds for A2
90 seconds
62
T/F absorbance is recorded at 27 seconds and again at 90 seconds during the BUN enzymatic reaction procedure
T
63
Sequence: Prepare sample and reagent
1 Mix the solution by inverting the tubes 2-3 times
2 Set up the spectrophotometer at 340 nm.
3 Feed the solution into the spectrophotometer at 27 seconds and record absorbance as A1
4 Start incubation time
5 Add the reagent by touching the pipet to the side of the tube
2 5 1 4 3
64
BUN Determination Assay requirements
Wavelength
Optical Path
Temperature
Wavelength: 340 nm
Optical path: 1 cm
Temperature: 37 ͦ C
65
Urea Nitrogen Reference Intervals
Plasma or Serum
6-20 mg/dL [CU]
2.1-7.1 mmol/L [SI]
66
Urea Nitrogen Reference Intervals
24-h Urine
12-20 g/day [CU]
0.43-0.71 mmol/day [SI]
67
Clinical Significance
Elevated urea concentration in blood
Azotemia
68
Clinical Significance
Increased urea level accompanied by renal failure
Uremia/Uremic Syndrome
69
Range of Ellitrol Assayed Chemistry Control Level 1 Urease & Indophenol
Urease : 13.3-17.7
Indophenol : 28.5-37.9
70
Range of Ellitrol Assayed Chemistry Control Level 2 Urease & Indophenol
Urease : 42.4-51.6
Indophenol : 90.7-111.0
71
Formula for BUN determination
(A1-A2) sample/(A1-A2) standard x 50
72
most widely used non-protein nitrogen compounds to assess renal function are __________ and __________
urea & creatinine
73
T/F uric acid is used to diagnose disturbances in purine metabolism (eg. gouty arthritis)
T
74
T/F: proteins are left in the specimen during the analysis of NPN compounds because they enhance the measurement.
F - removed because they interfere with analysis
75
Select: Lowest Plasma Concentration
A. Creatinine
B. Uric acid
C. Ammonia
D. Urea
C - 0.2%
76
C(BUN) = __________ x C(Urea).
0.466
77
Select: Reference intervals for BUN in adults for plasma/serum
A. 4-15 mg/dL
B. 6-20 mg/dL
C. 2.1-7.1 mmol/L
D. 10-25 mg/dL
B & C
78
Select: Post-renal increased plasma urea concentration
A. Urinary tract obstruction
B. Acute renal failure
C. Renal calculi
D. Tumor in the bladder
A C D
79
T/F Low protein intake and severe vomiting can cause a decrease in plasma urea concentration
T
80
Odd One Out: Pre-renal increased plasma urea concentration
A. Congestive heart failure
B. Renal disease
C. Dehydration
D. Shock
B - renal increased conc.
81
OOO: Direct method for measuring urea
A. Involves heating the sample with diacetyl monoxime
B. Lacks sensitivity
C. Involves enzymatic digestion of urea
D. Time-consuming
C. Involves enzymatic digestion of urea - indirect
82
indirect method for measuring urea involves digesting urea with the enzyme ___ to form ammonia, which is then measured
urease
83
T/F BUN value is typically higher than the urea value
F - lower
84
approximate BUN to urea ratio
1:2
