Non-Protein Nitrogens

Question 1

nitrogen compounds

Answer 1

protein
nucleic acids
non-protein nitrogen plasma concentrations

Question 2

non-protein nitrogens

Answer 2

urea 45-50%
amino acids 25%
uric acid 10%
creatinine 5%
ammonia 0.2%

Question 3

Blood Urea Nitrogen (BUN)

Answer 3

manipulation of ammonia from the break down of protein, conjugated into urea in liver
filtered by renal tubules w/ partial reabsorption
cannot be used in clearance testing bc of reabsorption

Question 4

BUN concentration depends on

Answer 4

renal function - if damaged BUN will be high
perfusion - sluggish blood flow BUN will be high
protein content of the diet
rate of protein catabolism

Question 5

azotemia (BUN increase)

Answer 5

pre-renal conditions
renal conditions
post renal conditions

Question 6

Pre-renal conditions for BUN increase

Answer 6

increased protein degradation - increase protein in diet, stress, fever, major illness, cortisol therapy
decreased blood flow through kidney- dehydration etc

Question 7

renal conditions for BUN increase

Answer 7

kidney diseases

inflammations

Question 8

post-renal conditions for BUN increase

Answer 8

blockages, obstructions
severe infections of kidney
tumors of bladder

Question 9

reasons for BUN decrease

Answer 9

low protein intake
severe liver disease
late in pregnancy
infancy 
not as significant as increased BUN

Question 10

BUN/ Creatinine ratios

Answer 10

normal ratio : 10-20
pre-renal BUN/creatinine increase ratio -creatinine is normal & BUN value is elevated
renal BUN/creatinine ratio normal- both markers are elevated but ratio is normal
post-renal BUN/creatinine ratio increased - rise in both but more in BUN
low protein diet - decreased ratio

Question 11

BUN analysis

Answer 11

coupled enzymatic reation - urease
patient’s urea + urease enzyme –> ammonia & carboxyl group
ammonia -(GLDH)-> NAD+
NAD is read at 340 nm to get BUN concentration

Question 12

BUN electrode method

Answer 12

urease breaks urea into ammonia & ammonia ions change conductivity of electrod
meter reads change in potential between standard & patient sample
calculates BUN in mg/dL

Question 13

BUN specimens

Answer 13

avoid ammonia, Na-citrate, Na-fluoride in samples
don’t need to be fasting
avoid bacterial contamination ( produce urease)
use plasma or serum
urines need to be diluted by 10

Question 14

Uric Acid

Answer 14

nucleic acid breakdown of purines (Adenine & guanine)
eliminated :
70% out kidneys
30% our GI

Question 15

hyperuricemia

Answer 15

elevated uric acid
gout- joint inflammation, uric acid crystals
F-1-PA: fructose 1 phosphate aldolase deficiency will cuase an increase in uric acid
Lesch-nyhan syndrome -missing HGPRT & cannot break down nucleic acids in a way that they can be reuesd

Question 16

hypouricemia

Answer 16

decreased uric acid
fanconi’s syndrome- tubule defect in the kidney & cannot reabsorb uric acid
drugs interfere w/ degradation process of nucleic acids & do not allow for uric acid to be formed

Question 17

Uric Acid analyzer methods

Answer 17

enzymatic method using uricase
uric acid from patient + uricase -> allantoin + peroxide+ co2
peroxidase reaction to make color rx
interference for peroxidase : 
ascorbic acid, bilirubin etc

Question 18

Uric Acid specimens

Answer 18

use heparinized plasma or serum NO EDTA
drugs like aspirin & thiazides - increase uric acid
lipemia, increased bilirubin, hemolysis etc- decrease uric acid due to interference

Question 19

creatinine

Answer 19

produced from creatine degradation in muscle tissue
creatinine level depends on muscle mass
plasma creatinine is inversely related to GFR

Question 20

eGFR

Answer 20

estimated GFR which accounts for age, gender, ethnicity

better indicator for early kidney disease

Question 21

Creatinine levels (low & high)

Answer 21

low levels are not significant in normal patients
high levels associated w/ increased blood creatinine & decreased GFR
although kidneys can have a 50% loss before any inrease in creatinine levels appear

Question 22

methods for creatinine analysis

Answer 22

kinetic jaffe reaction
colorimetric jaffe reaction
enzymatic reaction -automated methods
IDMS - isotope dilution mass spectroscopy

Question 23

Creatininease reaction

Answer 23

patient’s creatinine + creatininase enzyme -> creatine

creatine + CK -> phosphorylated creatine + PK -> pyruvate + LD -> NADP+ which is read at 340 nm

Question 24

Creatinine specimen

Answer 24

use plasma, serum, or urine
avoid hemolysis, icteric (high bilirubin) samples
fasting not required
high protein diet can cause transient increase in creatinine concentration
refrigerate urines - cut bacterial contamination

Question 25

sources of error in creatinine reaction

Answer 25

ascorbate, glucose, alpha keto acids, uric acid
bilirubin - negative bias in reactions
ascorbate interferes w/ peroxidase rx
cephalosporin - increases creatinine levels in jaffe reactions
dopamine & liodcaine - cause positive bias in enzymatic reactions

Question 26

Creatinine clearance calculation

Answer 26

VU/Px1.73/A
V- 24 hour urine volume
U-urine creatinine
P-plasma creatinine
A- body surface in meters2

Question 27

BUN range

Answer 27

7-18 mg/dL

Question 28

Creatinine range

Answer 28

male - 0.9-1.5 mg/dL

female - 0.7-1.3 mg/dL

Question 29

uric acid range

Answer 29

male - 3.5-7.2 mg/dL

female - 2.6-6.0 mg/dL