Non-Protein Nitrogen

Question 1

Nitrogen-containing compounds measured after removal of proteins in specimen.

Answer 1

NPN

Question 2

NPN is measured by converting nitrogen to ammonia and subsequent reaction with _______ (K2[Hgl4]) to form a yellow product measured.

Answer 2

Nessler’s reagent

Question 3

What are the specimen of NPN?

Answer 3

1. Urine
2. Plasma

Question 4

What is the % total NPN of excreted Urea in plasma?

Answer 4

45-50%

Question 5

What is the % total NPN of excreted Urea in urine?

Answer 5

86%

Question 6

Urea is also known as:

Answer 6

carbamide

Question 7

T/F:

Urea is the highest concentration in blood.

Answer 7

T

Question 8

T/F:

Urea is the major excretory product of protein metabolism.

Answer 8

T

Question 9

Chemical formula of Urea:

Answer 9

CO(NH2)2

Question 10

Clinical applications of Urea: (5)

Answer 10

1. Evaluation of renal function
2. Assess hydration status
3. Determination of nitrogen balance
4. Aid in the diagnosis of renal disease
5. Verify adequacy of dialysis

Question 11

Conversion factor of Urea (mg/dL to mmol/L):

Answer 11

0.357

Question 12

• Most frequently used method
• Uses urease enzyme to catalyze hydrolysis of urea and the liberated ammonium ion (NH4+) is quantified.

Answer 12

Enzymatic method

Question 13

BUN enzymatic method:

• most common assay
• best as a kinetic measurement

Answer 13

Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction

Question 14

BUN enzymatic method:

Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction measures the disappearance of:

Answer 14

nicotinamide adenine dinucleotide

Question 15

BUN enzymatic method:

GLDH measures rate of disappearance of nicotinamide adenine dinucleotide (reduced NADH) at _ nm

Answer 15

340 nm

Question 16

BUN enzymatic method:

Used in automated systems, multilayer film reagents and dry reagent strips, measures color change due to change in pH.

Answer 16

Indicator dye

Question 17

BUN enzymatic method:

• a specific and rapid test
• uses electrode to measure rate of increase in conductivity
• produced by ammonium ions

Answer 17

Conductometric method

Question 18

BUN enzymatic method:

• reference method
• uses isotopically-labeled compound for quantification
• detects characteristic fragments following ionization

Answer 18

Isotope Dilution Mass Spectrophotometry (IDMS)

Question 19

Specimen considerations in BUN:

Answer 19

1. Serum
2. Plasma
3. Urine

Question 20

What are the tubes should not be used in measuring BUN?

Answer 20

1. Sodium citrate (light blue)
2. Sodium fluoride (gray)

Question 21

What are the 3 urea reagent kit?

Answer 21

1. Reagent 1: R1 Tris buffer (pH 7.6), ADP, α-ketoglutarate, urease, glutamate dehydrogenase, sodium azide
2. Reagent 2: NADH, sodium azide (irritates eyes and skin)
3. Standard Urea: 50 mg/dL or 8.33 mmol/L (may vary depending on manufacturer)

Question 22

Assay requirements:

Wavelength

Answer 22

340 nm

Question 23

Assay requirements:

Optical path

Answer 23

1 cm

Question 24

Assay requirements:

Temperature

Answer 24

37 C

Question 25

# Assay requirements: Read against:

Answer 25

distilled water

Question 26

# Calculations: Conversion factor of BUN to Urea:

Answer 26

0.466 X Urea

Question 27

# Calculations: Conversion factor of Urea to BUN:

Answer 27

2.14 X BUN

Question 28

Reference interval of Plasma or Serum in Adults:

Answer 28

6-20 mg/dL

Question 29

Reference interval of 24-hour Urine in Adults:

Answer 29

12-20 g/day

Question 30

# Clinical significance: Elevated urea concentration in blood

Answer 30

Azotemia

Question 31

# Clinical significance: Increased urea level accompanied by renal failure

Answer 31

Uremia/Uremic Syndrome