[2S] UNIT 9.1 Urea Flashcards
Nitrogen-containing compounds measured after removal of proteins in specimen
Non-Protein Nitrogen
Measured by converting nitrogen to ammonia and subsequent reaction with Nessler’s reagent (K2[Hgl4]) to form a yellow product measured spectrophotometrically
Non-Protein Nitrogen
NPNs specimen
Serum, Urea & Plasma (SUP)
URINE OR PLASMA
Assesses the kidney
Both
URINE OR PLASMA
For urea concentration test
Urine
Also known as carbamide
Urea
Most abundant NPN (50%)
Urea
Produced in the liver from amino groups (-NH2) and free ammonia
Urea
Major excretory product of protein metabolism
Urea
Chemical formula of Urea
CO(NH2)2
CLINICAL APPLICATIONS
Evaluation of renal function
Urea
CLINICAL APPLICATIONS
Assess hydration status
Urea
CLINICAL APPLICATIONS
Determination of nitrogen balance
Urea
CLINICAL APPLICATIONS
Aid in the diagnosis of renal disease
Urea
More appropriate term for quantification of urea
Blood Urea Nitrogen (BUN) Determination
CLINICAL APPLICATIONS
Verify adequacy of dialysis
Urea
T/F: DIALYSIS - ↑ BUN = dialysis isn’t compensating
T
Conversion factor of BUN (mg/dL to mmol/L)
0.357
BUN DETERMINATION
Most frequently used method
Enzymatic Method
BUN DETERMINATION
Uses urease enzyme to catalyze hydrolysis of urea and the liberated ammonium ion (NH4
+) is quantified.
Enzymatic Method
BUN DETERMINATION
Most common assay
ENZYMATIC: Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
BUN DETERMINATION
Best as a kinetic measurement
ENZYMATIC: Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
BUN DETERMINATION
Measures rate of disappearance of nicotinamide adenine dinucleotide (NADH) at 340 nm
ENZYMATIC: Glutamate dehydrogenase (GLDH)-coupled enzymatic reaction
BUN DETERMINATION
Used in automated systems, multilayer film reagents and dry reagent strips
ENZYMATIC: Indicator Dye
BUN DETERMINATION
Measures color change due to change in pH
ENZYMATIC: Indicator Dye
BUN DETERMINATION: ENZYMATIC
T/F: NADH is indirectly proportional to ammonia
F; directly (ammonia originates from the urea)
BUN DETERMINATION
A specific and rapid test
ENZYMATIC: Conductometric
BUN DETERMINATION
Uses electrode to measure rate of increase in conductivity produced by ammonium ions
ENZYMATIC: Conductometric
BUN DETERMINATION
Reference method
ENZYMATIC: Isotope Dilution Mass Spectrometry (IDMS)
BUN DETERMINATION
Used isotopically-labeled compound for quantification
ENZYMATIC: Isotope Dilution Mass Spectrometry (IDMS)
BUN DETERMINATION
Detects characteristic fragments following ionization
Isotope Dilution Mass Spectrometry (IDMS)
T/F: Urine should be diluted
T bcs mas maraming urea sa urine
Dilution factor of Urine
1:20 with NSS
Irritate the eyes and skin
Reagent 2: NADH, sodium azide
Standard urea
50 mg/dL or 8.33 mmol/L (may vary depending on manufacturer)
What type of urine is refrigerated?
24 hr urine sample
For the reduction of NADH to NAD (reagent)
Reagent 2: NADH, sodium azide
5 Reagent 1
RAUGAS
R1 Tris buffer (pH 7.6)
ADP
urease
glutamate
α-ketoglutarate
sodium azide
_ absorbance = ↑ conc. of urea
↓
ASSAY REQUIREMENTS
Wavelength: ____
Optical path: ____
Temperature: ____
Read against ______ _____
Wavelength: 340 nm
Optical path: 1 cm
Temperature: 37 ͦC
Read against distilled water
Conversion factor of urea to BUN
0.466 x C (Urea)
Conversion factor of BUN to urea
2.14 x C (BUN)
Reference intervals for BUN in adults’ plasma / serum
CU = 6-20 mg/dL
SI = 2.1-7.1 mmol/L
Reference intervals for BUN in adults’ 24 hr urine
CU = 12-20 g/day
SI = 0.43-0.71 mmol/day
Elevated urea concentration in blood
Azotemia
Increased urea level accompanied by renal failure
Uremia / Uremic Syndrome
Before the kidney
Pre-Renal
Most of the time due to reduced renal blood flow
Pre-Renal
Less renal blood delivered to the kidney, less urea filtered and excreted in the kidney; increased urea levels
Pre-Renal
↑ Urea & Normal Creatinine
Pre-Renal
↑ Urea & Creatinine
Renal
Normal Urea & ↑ Creatinine
Post-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
● Congestive heart failure
● Shock
Pre-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
● Hemorrhage
● Dehydration
Pre-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
Increased protein catabolism
Pre-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
High-protein diet
Pre-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
Acute and chronic renal failure
Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
Renal disease (glomerular nephritis and tubular necrosis)
Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
Urinary tract obstruction
Post-Renal
CAUSES OF ABNORMAL PLASMA UREA CONC
● Renal calculi
● Tumor in the bladder or prostate
● Severe infections
Post-Renal
T/F: DECREASED CONCENTRATION
The decrease of urea in the body is due to the slow metabolism of proteins in the body
T
CAUSES OF ABNORMAL PLASMA UREA CONC
Low protein intake
Decreased Concentration
CAUSES OF ABNORMAL PLASMA UREA CONC
Liver disease
Decreased Concentration
CAUSES OF ABNORMAL PLASMA UREA CONC
Severe vomiting and diarrhea
Decreased Concentration
CAUSES OF ABNORMAL PLASMA UREA CONC
Pregnancy
Decreased Concentration
BUN:Urea ratio
1:2
Measures the amount of nitrogen in your blood that comes from the waste product Urea
BUN Test
PROCEDURE
Read Absorbance 1 (A1) at ___?
27 secs
PROCEDURE
Set-up the spectrophotometer at _____ wavelength
340 nm
PROCEDURE
Continue the timer and read Absorbance 2 (A2) at
exactly?
90 seconds
Not excreted in urine
Amino acids
Reabsorbed immediately by the proximal convoluted chain through active transport
Amino acids
Urea cycle in what organ
Liver
Due to the reduced renal function that causes an increase in plasma concentration as a result of compromised urea excretion
Renal
Problem in filtering the urea because of issues in the glomerulus
Renal
Most likely due to the obstruction of urine flow in the urinary tract
Post-Renal
After the kidney
Post-Renal
Measures a chromogen produced directly from Urea
Direct Method