Non-Protein Nitrogen

Question 1

Ammonia

Answer 1

NH3; used to make urea in the liver during the urea cycle

Question 2

Azotemia

Answer 2

high concentration of urea in blood;

Question 3

Coupled Enzymatic method

Answer 3

urea + 2H2O –> urease–>2NH4+ +CO32-; NH4+ + 2-oxoglutarate –>GLDH–>glutamate + H20;

Question 4

creatine

Answer 4

formed in liver from arginine, glycine, and methionine; converted to creatine phosphate which is a high energy source

Question 5

creatinine

Answer 5

formed from creatine and creatine phosphate in muscle; excreted into plasma at a constant rate; used to assess kidney function

Question 6

creatinine clearance

Answer 6

a measure of the amount of creatinine eliminated from the blood by the kidneys; CrCl = U(cr)V(u)/P(cr)t

Question 7

estimated glomerular filtration rate

Answer 7

eGFR(mL/min/1.73m^2) = 175 x (Scr)^-1.154 x (age)^-.203 x (0.742 if female) x (1.210 if African-american)

Question 8

glomerular filtration rate (GFR)

Answer 8

volume of plasma filtered by the glomerulus per unit of time

Question 9

gout

Answer 9

caused by hyperuricemia; too much uric acid in body and uric acid crystals form and build up in joints, fluids, and tissues

Question 10

hyperammonemia

Answer 10

excess if ammonia in the blood; leads to brain injury and death; primary cause of neurologic disorders

Question 11

hyperuricemia

Answer 11

abnormally increased plasma uric acid concentrations; gout, increased catabolism of nucleic acids (chemotherapy), and renal disease; toxemia in pregnancy (decreased excretion)

Question 12

hypouricemia

Answer 12

severe liver disease, rarer than hyperuricemia; Fanconi syndrome, chemotherapy with inhibitors of purine symthesis;

Question 13

decreases in plasma urea

Answer 13

low protein intake, severe vomiting and diarrhea, liver disease, and pregnancy; low urea N/creatinine ratio

Question 14

protein-free filtrate

Answer 14

measurement of non-protein nitrogen; used in caraway method which oxides uric acid in this filtrate

Question 15

uric acid

Answer 15

product of catabolism of the purine nucleic acids; relatively insoluble in plasma; at high concentrations can be deposited in the joints and tissues

Question 16

decreases in plasma urea

Answer 16

low protein intake, severe vomiting and diarrhea, liver disease, and pregnancy; low urea N/creatinine ratio

Question 17

measurement of uric acid

Answer 17

uric acid –>uricase–>allantoin +CO2+2 H2O2; difference in absorbance before and after incubation with uricase is proportional to uric acid concentration; protein cause high background; hemoglobin and xanthine cause negative interference

Question 18

measurement of uric acid

Answer 18

uric acid –>uricase–>allantoin +CO2+2 H2O2; difference in absorbance before and after incubation with uricase is proportional to uric acid concentration; protein cause high background; hemoglobin and xanthine cause negative interference

Question 19

Jaffe Reaction

Answer 19

creatinine + picrate –>red-orange complex; positive bias from ascorbic acid, glucose, glutathione, alpha-keto acids, uric acid, and cephalosporins

Question 20

Jaffe with adsorbent

Answer 20

creatinine adsorbed onto fuller’s earth then reacted with alkaline picrate –> colored complex; improves specificity

Question 21

Jaffe with adsorbent

Answer 21

creatinine adsorbed onto fuller’s earth then reacted with alkaline picrate –> colored complex; improves specificity

Question 22

endpoint Jaffe method

Answer 22

sample heated in acid solution to convert creatine to creatinine for measurement

Question 23

Creatine enzymatic methods

Answer 23

creatine kinase, pyruvate kinase, and lactate dehydrogenase are used to produce a colored product

Question 24

clinical application of urea measurement

Answer 24

to assess renal function, hydration status, determine nitrogen balance, aid in renal disease diagnosis, verify dialysis

Question 25

Urea N calculation (US)

Answer 25

1 mg urea N/dL x 1 mmol N/14 mg N x 1 mmol urea/2 mmol N x 60 mg urea/1 mmol urea = 2.14 mg urea/dL

Question 26

Urea N calculation (SI)

Answer 26

mg/dL * 0.36 = mmol/L

Question 27

Reference Intervals - Adult; plasma

Question 28

Reference Intervals- Adult, Urine

Answer 28

12-20 g/d; 0.43-0.71 mol urea/d

Question 29

urea nitrogen/creatinine ratio

Answer 29

used to differentiate cause of abnormal urea concentration