Non-Protein Nitrogen Flashcards
Nitrogen-containing compounds measured after removal of proteins in specimen.
NPN
NPN is measured by converting nitrogen to ammonia and subsequent reaction with _______ (K2[Hgl4]) to form a yellow product measured.
Nessler’s reagent
What are the specimen of NPN?
- Urine
- Plasma
What is the % total NPN of excreted Urea in plasma?
45-50%
What is the % total NPN of excreted Urea in urine?
86%
Urea is also known as:
carbamide
T/F:
Urea is the highest concentration in blood.
T
T/F:
Urea is the major excretory product of protein metabolism.
T
Chemical formula of Urea:
CO(NH2)2
Clinical applications of Urea: (5)
- Evaluation of renal function
- Assess hydration status
- Determination of nitrogen balance
- Aid in the diagnosis of renal disease
- Verify adequacy of dialysis
Conversion factor of Urea (mg/dL to mmol/L):
0.357
- Most frequently used method
- Uses urease enzyme to catalyze hydrolysis of urea and the liberated ammonium ion (NH4+) is quantified.
Enzymatic method
BUN enzymatic method:
- most common assay
- best as a kinetic measurement
Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
BUN enzymatic method:
Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction measures the disappearance of:
nicotinamide adenine dinucleotide
BUN enzymatic method:
GLDH measures rate of disappearance of nicotinamide adenine dinucleotide (reduced NADH) at _ nm
340 nm
BUN enzymatic method:
Used in automated systems, multilayer film reagents and dry reagent strips, measures color change due to change in pH.
Indicator dye
BUN enzymatic method:
- a specific and rapid test
- uses electrode to measure rate of increase in conductivity
- produced by ammonium ions
Conductometric method
BUN enzymatic method:
- reference method
- uses isotopically-labeled compound for quantification
- detects characteristic fragments following ionization
Isotope Dilution Mass Spectrophotometry (IDMS)
Specimen considerations in BUN:
- Serum
- Plasma
- Urine
What are the tubes should not be used in measuring BUN?
- Sodium citrate (light blue)
- Sodium fluoride (gray)
What are the 3 urea reagent kit?
- Reagent 1: R1 Tris buffer (pH 7.6), ADP, α-ketoglutarate, urease, glutamate dehydrogenase, sodium azide
- Reagent 2: NADH, sodium azide (irritates eyes and skin)
- Standard Urea: 50 mg/dL or 8.33 mmol/L (may vary depending on manufacturer)
Assay requirements:
Wavelength
340 nm
Assay requirements:
Optical path
1 cm
Assay requirements:
Temperature
37 C
Assay requirements:
Read against:
distilled water
Calculations:
Conversion factor of BUN to Urea:
0.466 X Urea
Calculations:
Conversion factor of Urea to BUN:
2.14 X BUN
Reference interval of Plasma or Serum in Adults:
6-20 mg/dL
Reference interval of 24-hour Urine in Adults:
12-20 g/day
Clinical significance:
Elevated urea concentration in blood
Azotemia
Clinical significance:
Increased urea level accompanied by renal failure
Uremia/Uremic Syndrome
