Lec 11: NPN

Question 1

What are the clinically significant NPN compounds?

Answer 1

• Urea
• Amino acids
• Uric acid
• Creatinine
• Creatine
• Ammonia

Question 2

UREA

Plasma conc: ___
Urine conc: ___

Answer 2

Plasma conc: 45-50
Urine conc: 86

Question 3

URIC ACID

Plasma conc: ___
Urine conc: ___

Answer 3

Plasma conc: 10
Urine conc: 1.7

Question 4

CREATININE

Plasma conc: ___
Urine conc: ___

Answer 4

Plasma conc: 5
Urine conc: 4.5

Question 5

AMMONIA

Plasma conc: ___
Urine conc: ___

Answer 5

Plasma conc: 0.2
Urine conc: 2.8

Question 6

AMINO ACID

Plasma conc: ___

Answer 6

Plasma conc: 25

Question 7

CREATINE

Plasma conc: ___

Answer 7

Plasma conc: 1 to 2

Question 8

The most abundant waste product in the body. It has the highest concentration in the plasma and urine.

Answer 8

Urea

Question 9

The major excretory product of protein metabolism.

Answer 9

Urea

Question 10

Where does the Urea Cycle occur?

Answer 10

Hepatocytes/Liver cells

Question 11

Its goal is to convert ammonia into a less toxic urea. It’s an important pathway to reduce levels of ammonia in the blood

Answer 11

Urea cycle

Question 12

UREA

Chemical method: ___
Enzymatic method: ___

Answer 12

Chemical method:
• Diacetyl monoxime

Enzymatic method:
• Urease
• Coupled Urease with GLDH

Question 13

Color result of DAM

Answer 13

Yellow

Question 14

Wavelength used in DAM method

Answer 14

540 nm

Question 15

In enzymatic method using urease, what product was quantified?

Answer 15

Ammonia or Ammonium ion

Question 16

Coupled urease with GLDH is also known as ___

Answer 16

Berthelot method

Question 17

In coupled urease with GLDH, what was the wavelength used?

Answer 17

340 nm

Question 18

The reference method (gold standard) for urea, uric acid, and creatinine.

Answer 18

IDMS

Question 19

Conversion factor:
BUN mg/dL to urea mg/dL

Answer 19

2.14

Question 20

Conversion factor:
BUN mg/dL to Urea mmol/L

Answer 20

0.357

Question 21

False negative or positive?

In Urea, using sodium citrate & sodium fluoride as anticoagulant.

Answer 21

NEGATIVE

• it inhibits urease

Question 22

False negative or positive?

In Urea, using hemolyzed samples.

Answer 22

POSITIVE

• RBCs contain urea inside

Question 23

False negative or positive?

In Urea, using samples contaminated with bacteria.

Answer 23

NEGATIVE

• Bacteria produce their own urease and will convert urea on their own.

Question 24

When collecting plasma samples for UREA, what anticoagulants are AVOIDED and USED?

Answer 24

MAY USE:
lithium & sodium heparin

AVOID:
Sodium citrate & sodium fluoride
- inhibits urease
- false negative
ammonium heparin
- false positive

Question 25

**UREA** reference ranges

Answer 25

6–20 mg/dL 2.1–7.1 mmol/L

Question 26

Prerenal azotemia

Answer 26

Increase of plasma urea as a result of reduced renal blood flow, which is caused before the kidney.

Question 27

Postrenal azotemia

Answer 27

Increase of urea concentration in the plasma due to obstruction of urine flow, which occurs after the kidney.

Question 28

Low protein intake & severe liver disease can cause major _____ in plasma urea concentration. (Increase or Decrease)

Answer 28

DECREASE

Question 29

**URIC ACID** is a final product of _____

Answer 29

Catabolism of purine nucleic acids

Question 30

Uric acid is the major product of catabolism of what purine nucleosides?

Answer 30

Adenosine, Guanosine

Question 31

Approximately ___% of Uric acid excreted is lost in the urine. While proximal tubules reabsorb ___% of uric acid.

Answer 31

70% 98–100%

Question 32

Uric acid is ___ in urine, while it is ___ in the blood. (Soluble, insoluble)

Answer 32

pKa of Uric acid: 5.75 Urine: insoluble - urine pH is near 5.75 Blood: soluble - blood pH is 7.35–7.45

Question 33

Nearly all Uric acid in plasma is present as ___.

Answer 33

Monosodium urate

Question 34

1. Define Hyperuricemia. 2. Causes

Answer 34

1. Increase uric acid in blood. 2. Excess dietary purine intake, chemotherapy

Question 35

Define Hyperuricosuria.

Answer 35

Increase of uric acid in urine

Question 36

**URIC ACID** 1. Chemical method • color result 2. Enzymatic method • give the wavelength used

Answer 36

1. Phosphotungstic acid (caraway method) • tungsten blue 2. Uricase, couple uricase with peroxidase/catalase • 293 nm, 548 nm

Question 37

Abnormally increased plasma uric acid concentration is seen in ____ wherein there is: • crystallization of uric acid (sodium urate) • found primarily in men • commonly affects big toe • in women, rises after menopause

Answer 37

Gout

Question 38

The following causes what NPN compound to increase? • hemolytic/megaloblastic anemia • starvation • chemotherapy • purine-rich diet

Answer 38

Uric Acid

Question 39

An X-linked genetic disorder caused by **deficiency of hypoxanthine-guanine phosphoribosyltransferase**. Seen ONLY in males.

Answer 39

Lesch-Nyhan Syndrome

Question 40

_False *negative* or *positive*?_ In uric acid, using hemolyzed samples.

Answer 40

NEGATIVE • when RBCs burst, it causes serum dilution.

Question 41

_False *negative* or *positive*?_ In uric acid, using samples with high bilirubin concentration.

Answer 41

NEGATIVE

Question 42

What drugs increase values for Uric Acid?

Answer 42

Salicylates, Thiazides

Question 43

When collecting plasma samples for Uric Acid: 1. what anticoagulants are AVOIDED? 2. False *negative* or *positive*?

Answer 43

1. EDTA, fluoride additives - inhibit uricase 2. NEGATIVE

Question 44

What causes decrease in Plasma Uric Acid concentration?

Answer 44

• liver decease • allopurinol over treatment • Fanconi syndrome - defective tubular reabsorption causes ALL URIC ACID to go to urine, and nothing to the blood.

Question 45

- Formed from creatine and creatine phosphate. - excreted at a constant rate.

Answer 45

Creatinine

Question 46

Plasma creatinine is ____ proportional to Glomerular Filtration Rate.

Answer 46

Inversely. • kidney working well = more filtration = low plasma creatinine

Question 47

1. Immediate precursor of creatinine? 2. Based on #1's answer, from what organs is it synthesized? 3. After synthesis, where is it transported to?

Answer 47

1. Creatine 2. Liver, pancreas, kidney 3. Muscles

Question 48

**CREATININE** 1. Chemical method • color result • wavelength used • interferences 2. Enzymatic method

Answer 48

1. Jaffe's method (alkaline picrate sol) • red orange chromogen (Janovski complex) • 490–505 nm • acetoacetate, glucose, acetone, pyruvate, ascorbate 2. Creatininase-Hydrogen Peroxide, Creatininase-Creatine Kinase

Question 49

**CREATININE** 1. What anticoagulants are USED? 2. What _KIND_ of samples are AVOIDED?

Answer 49

1. Sodium & lithium heparin 2. Icteric, hemolyzed, lipemic • false negative